What Should I Study?

I have a rating of 804 and will be competing in a state tournament soon. So what should I study?

Tactics, basic openings and basic endgames. 

You don't need to know how to checkmate with Knight and bishop vs king, but you need to know basic mates (Queen vs King, Rook vs King) pawn(s) and king vs king endings. In some cases you can win, in others you can only draw. You need to know what you must play if you are the attacker and if you are the defender. 

No need to learn extremely complicated openings with tens of variations, but you need to know at least some basic openings with maybe a couple variations. 

Spanish, Sicilian and Giuoco Piano are probably the most popular openings for e4.

Remember the basic principles of the opening: Center control with the pawns, develop your pieces, castle, do not play the queen way too early. 

If you follow those principles you will be Ok in most cases.  

And most importantly, solve problems. Try to develop the ability to see winning combinations. 

Thank you !! Which variations should I study in the Piano and Spanish ( is this also called the Ruy Lopez?)

If the tournament is within a week, there's nothing you can do seriously improve your playing strength. If you're rated 800, don't expect to win prizes or anything - just play your best, and try to get the most out of every game. In particular:

*Don't hang your pieces - before you decide to move, see what your opponent can do in response.

*Don't overlook the opponent's hanging pieces - your opponents will likely make many mistakes, so you need to be aware of them.

*Don't resign - For you, there should be no such thing as resignation. Play each game out to the end, even if you're getting checkmated K+Q vs Q. Who knows, maybe your 800 opponent will stalemate.

Also, I noticed you just joined this site 40 minutes ago, and somehow you're already on the forums. Just a note...

The tournament is March 18 so i have about a month to prepare. I joined Chess.com because I wanted advice.

I see. In that case I would recommend reading "Back to Basics: Tactics" by Dan Heisman, and doing exactly what he recommends in that book, word for word. That's probably the easiest way for you to get rapid improvement, because at the 800 level (which you will not be at anymore after a month of studying that book seriously) simple tactics and hanging pieces decide games almost always.

That one book is all I would recommend. It's great because Dan Heisman can't help himself - he has to include strategies on how to improve your overall chess, even in a book on tactics. 

The second book I'd recommend is "General Chess Improvement - the best of Novice Nook" for your long-term chess improvement. This book has things applicable to you, but will continue to be applicable as you improve. It's also by Dan Heisman. 

303 tricky chess tactics is a good place to start. It's basically a puzzle book, and who doesn't like puzzles? Also play lots of 15-60 minute practice games online. The shorter games wont help as much. Lastly watch strong players play blitz on youtube. Just seeing how they play their games can be a huge help.

Back to Basics: Tactics by Dan Heisman

https://web.archive.org/web/20140708233537/http://www.chesscafe.com/text/review585.pdf

https://www.newinchess.com/Shop/Images/Pdfs/2722.pdf

A Guide to Chess Improvement by Dan Heisman (2010)
https://web.archive.org/web/20140708105628/http://www.chesscafe.com/text/review781.pdf

303 Tactical Chess Puzzles by Fred Wilson & Bruce Albertson

https://web.archive.org/web/20140708100505/http://www.chesscafe.com/text/review320.pdf

303 More Tricky Chess Puzzles by Fred Wilson & Bruce Alberston

https://web.archive.org/web/20140708085526/http://www.chesscafe.com/text/review514.pdf

Possibly of interest:
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
https://www.newinchess.com/Shop/Images/Pdfs/7192.pdf
Logical Chess: Move by Move by Irving Chernev (1957)
https://web.archive.org/web/20140708104437/http://www.chesscafe.com/text/logichess.pdf
The Most Instructive Games of Chess Ever Played by Irving Chernev (1965)
https://chessbookreviews.wordpress.com/tag/most-instructive-games-of-chess-ever-played/
Winning Chess by Irving Chernev and Fred Reinfeld (1949)
https://web.archive.org/web/20140708093415/http://www.chesscafe.com/text/review919.pdf
Discovering Chess Openings by GM John Emms (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
Openings for Amateurs by Pete Tamburro (2014)
http://kenilworthian.blogspot.com/2014/05/review-of-pete-tamburros-openings-for.html

https://chessbookreviews.wordpress.com/tag/openings-for-amateurs/

https://www.mongoosepress.com/excerpts/OpeningsForAmateurs%20sample.pdf

Chess Endgames for Kids by Karsten Müller (2015)

https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
http://www.gambitbooks.com/pdfs/Chess_Endgames_for_Kids.pdf

Post #9 gives the links to everything you need, although I'd personally pick one of those, because you only have a month. 

And unfortunately most of those books in #10 should be reserved for people with 4 digit ratings. 

"Simple Attacking Plans is an ideal book for a beginner or casual player who wants to become acquainted with some standard attacking motifs. ..." - Michael McGuerty (2013)

https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf

You may be right on that one^. The game in the PDF demo is exactly the kind of game the OP may encounter in the tournament.

I assume you mean 804 in USCF. Honestly, at that level, just work on not blundering away the game with a single oversight. If your tactics suck, do your best to steer positions away from tactical opportunities for your opponent. For example don't keep your queen on the same file or rank as your opponent's rook -- no matter how many pieces are between them. Don't keep your queen on the same diagonal as their bishop. Push your pawns to form such a structure to keep out your opponent's knights. Knights are by far the trickiest piece in the game -- don't give them any targets to jump around each move because when they can move 2 or 3 times in a row with tempo, they'll deliver a devastating blow. In the opening, as a general rule of thumb, don't be the first to take a pawn with your own pawn. Rather push pawns that will improve the position of your pieces. Let the pawns pile up in the middle and let your opponent take your pawn with their pawn. Most of the time, they will weaken their position by initiating pawn trades. In general, have your pawns take back toward the middle of the board unless you see a good reason not to. Castle as early as possible and don't be too greedy in the opening, there's many gambits out there which give up pawns in exchange for tempo. Try to steer away from gambits, don't play into your opponent's hands by playing a line they prepared before hand, make them have to calculate just like you by playing a position you feel comfortable in. Don't be afraid to switch up your openings, whatever you feel comfortable with at a given time is the best opening to play. If you find yourself in a tight position with no room to move around your pieces, try to trade off material so you have less pieces to be trapped in that tight space. Don't be quick to overextend your pieces either. Overextended your pieces is bad too because if they extend too far, it can be hard to guard pieces far away from your side of the board, and if your opponent gets any piece into your territory, they can cause a lot of mayhem without any pawns there to kick them out. Keep in mind that the knight is a short range piece and the bishop is a long range piece. While the knight can attack any square on the board with enough moves, the bishop is limited to half the board based on its color. When you have the bishop pair, together they can take care of any problem square on the board. But once you trade either bishop, keep in mind that you become that much weaker on that color. Your opponent can simply put all their pieces on light squares if your bishop is stuck on dark squares rendering your bishop completely useless. IM Yaacov Norowitz has a great video on chess harmony. It's a good concept to keep in mind during your games. Also keep in mind every chess game has a critical move where it's like the whole game is decided in that one move. Recognize when a game hits a critical move and make sure to spend extra time before making a critical move. In general, improving your tactics will make you a better chess player. But position chess is just as important. Know when to resist tempting moves like taking a pinned knight with your bishop. Unless it prevents your opponent from castling, you're only giving up a well placed bishop for a poorly placed knight. A piece is only as good as the squares as it can move to. If a rook can move on any rank or file, but is trapped on the edge of the board by two pawns, it's no longer a piece that can move to any rank or file, it's a piece that can only take one pawn or the other and is worth no more than the pawn it sacrifices itself for. Recognize outposts on the board where you can place your knight because if your opponent can't push a pawn to chase your knight away, it's just a monstrous piece on the board which your opponent can't do anything about. Recognize when you have a passed pawn on the board. A passed pawn is a pawn you can push and there is no pawn on your opponent's side which can stop it from being pushed or challenge it from either side. If your opponent puts a piece in front of your passed pawn, make it your mission to take any piece they put in front of your pawn, even if you have to sacrifice the exchange in certain positions, that way you can push your pawn again. When you have a passed pawn, put your rook behind it. Don't let your opponent put their rook behind it first. But if they put their rook in front of it, that's fine. If your opponent creates a passed pawn, put a piece in front of it so they can't push it. Keep your eyes constantly peeled for back-rank weaknesses, both in your camp and your opponent's camp. Failure to see a checkmate by a rook or queen placed in the bank-rank is a common blunder made by new chess players. If you see your camp has a back rank weakness and the position is starting to look like a combination might be possible for your opponent to threaten a mate with it, don't be afraid to push a pawn near your king to give your king a flight square to take away any tactical potential in the position that your opponent might be able to exploit. Be cautious in openings of bishop + knight, bishop + queen, and queen + knight attacks. Don't push any of the three pawns near your king unless you know what you're doing because it weakens your king's position. Even if you fianchetto your bishop, if your bishop is ever traded, your pawn structure now creates two outposts for your opponent's pieces which can be hard to chase away. In general, don't try to checkmate a castled king with only two pieces. Also don't castle onto a side where your opponent has advanced a lot of pawns because they can easily break into the pawn structure surrounding your king, opening up your king to checks. If the pawns around your king are ever weakened to the point that you have to be on the constant look out for checks, make it your duty to trade queens. Once queens have been traded, both kings can sit relatively close to the middle of the board without many problems. In general, don't push your king into your opponent's pawns as it's easy to get mated if you don't know what you are doing. The exception, of course, is if you're able to take a base pawn and cause your opponent's pawn structure to fall. When you see a good move in a position look for an even better move. Also when you see a threat your opponent is making, look to see if there are any more threats also being made. A common mistake is to see a pawn being threatened but miss a more valuable piece also being threatened like a knight, rook, or queen. Make sure you're able to find the biggest threat in a given position. Some positions can have more than two threats being made in the same move. When you get stuck on the defending side of the board, keep in mind the best defense is simply to trade down your opponent's power. But don't make foolish moves offering a trade they can easily avoid. Always see the threats they are making and address those first. Whenever you make a move, always double check it if it creates a weakness. For example, you may have a pawn guarding your knight, but also want to push a pawn to chase away a bishop. But by pushing the pawn, you also take away the defender of your knight so your opponent can simply take the knight with their bishop. Don't make this blunder. Also, don't push the edge pawn near your castled king if your opponent can sacrifice a bishop for the edge pawn and take the pawn you took back with using their queen. This sacrifice is deadly, even if attempted prematurely with no follow-up. Sacrificing a bishop for two pawns near a king with a queen on the board able to start checking the king is more than enough compensation for the sacrifice. Be aware of this tactic and don't fall prey to it. Also be cautious of any queen or rook on the same file or rank as your king, and any queen or bishop on the same diagonal as your king. If a pawn is pinned to your king, it's unable to protect anything. For example if your opponent has a rook pinning a pawn to your king, and that pawn protects a knight. Then that knight is unprotected, and your opponent can even take it with a queen and you will be unable to take the queen with your pawn because it is pinned to your king. As you play more chess you'll get better and start recognizing patterns easier. For example a knight might be a short range piece, but it takes four moves for a knight to move to the square two diagonals over. So, for example, if your opponent checks you with their knight and you want to find the safest place to put your king so their knight can't check you any more, that is the square. In general, the more time you invest into chess, the better the player you become. There are many types of chess games you can player. You can player bullet games where you need to move as fast as possible to win. You probably won't learn much from such games though. Blitz games I think are a great way to improve as a chess player. They are fast enough to challenge your chess understanding, but slow enough for you to think before you move on critical positions. Longer games such as standard time controls can be a time burden, and you probably won't learn as much from such games for your time investment. But if you have a lot of time to invest, playing longer games is a great way to explore new lines so you can put as much thought as you need into each move to produce your own opening system. Once you have a decent opening system, play blitz chess to become more efficient at making your moves for the opening system you learned. Making moves efficiently is important because it puts more pressure on your opponent to move quickly, and it gives you more time to think in critical moves of the game. Hope you'll learned something from this post. Cheers!

Keep it simple - I'm not sure the OP will be able to apply everything you've said above. 

And no blitz chess, in my opinion. Blitz chess is not going to help you in your classical tournament.