What is the number one thing beginners/intermediates need to improve on?

What is the number one thing beginners and intermediates fail to work on and as a result their play never gets better? 

And how do you work on the thing(s) that need to be improved? 

Tactics probably. And to recognize that they are "Hope Chess" players (much like I am ) and to strive to fix this. 

If you are not aware of what a "Hope Chess" player is, it is someone who makes useless threats in the hope that the opponent does not make the best move, which will almost always improve his position more than yours.

Well, being one of the players in this category I can say that end games and tactics are never studied enough. I've found that I'm more confident at the board against similar rated players when I feel that I'm up on my end game knowledge. For beginnings I always just use sound opening principles and don't always use a book opening. In my opinion, tactics and end game knowledge should be what is studied. Too many players, I think, study openings but don't know how to finish games.

That's my thought on this subject though. Have a great day!

For beginners, looking at the board after their opponent's move, and look if any thing is under attack in their territory : "What's the threat ? What is he trying to do ? What would happen if I passed ?"

For intermediate players, it depends.

Exactly. Beginners must give up "hope".

Just thinking about your own moves without trying to find the best reply for the opponent, a similar thing to 'hope chess' but more insidious because its a lazy way of thinking. Some top players based their whole strategy on looking at what their opponent would like to do and simply preventing them from doing it. Its not sexy but its a perfectly reasonable way to play.

Number one priority, study their completed games. All outlined in my free video lessons course on my website.

Superficial aggressive moves or unsound sacrificial ideas that only work if the opponent misses something but give you a cheap thrill playing them.

Some people are only interested in 'exciting' chess, thats why blitz and bullet is so popular. The quality of the moves is irrelevant, just the buzz of being under time pressure or having made an unclear sacrifice that just might lead to a brilliancy..its an adrenaline rush I guess, I doubt whether they play over Petrosian or Karpov games too often.

Beginners: Look at the board, all 64 squares, with an eye for offence and defence. Look at the board.

Intermediate: Study opening and endgame theory; and play over the board games for experience. Play games with higher ranked players and study post game analysis.

Sorry onthehouse, I´m stealing your idea:

Beginners: Look at the board, all 64 squares, with an eye for offence and defence.

Intermediates: Look at the board, the 32 most important squares, and develop a plan which won´t lose you any pieces.

Experts: Look at the board, the 16 most important squares, and decide upon which one you intend to attempt to deliver checkmate.

Carlsen: Look at the board, all 64 squares except for the one where you know that you´ll deliver checkmate in 23 moves, and wonder where the nearest McDonalds is.

Basic principle for all: look at the board!

Actually, that's not at all what "Hope Chess" means, as Dan Heisman uses the term. It means somebody who doesn't look for their opponent's checks, captures and threats, and waits until after the opponent has moved to see if they can meet any threats that they've made.

Here is the source: http://www.chesscafe.com/text/real.pdf See page 2 for his definition.

Recognizing tactics is probably the route to quickest improvement up until ~1500, followed by endgames.

I would say restrain yourself. Stop, look, and think ahead before you move and piece.  Dont go for "fool's mate" plan for  long games.

I apologize sapientdust, it's been a while since I've read some of his articles. 

You may be able to notice similiar ideas between the two. More often than not, an opponent's best move is a threat that cannot be met, and ignoring this falls under the definition of a "Hope Chess" player. 

Tactics.  Also, I noticed lower-rated players are too cautious, playing defensively at any hint of attack but that just shows lack of tactical confidence.  You gotta be brave but to brave you need to be good at tactics.

Judging by half the ones I meet on chess.com,---- their manners!!

@Tjornan, it's a common misconception. Heisman explicitly states in that article that it's not what you said, because it is in fact what many people commonly remember. It's an easy mistake to make, because hoping your opponent doesn't see your threats is the first kind of hope that comes to mind when you think of rank beginners and how they play. Perhaps a different name would have been better than "Hope Chess" in retrospect, since there are two kinds of hope beginners commonly engage in, and the one Dan doesn't mean is the one that comes to mind most easily. I think though that hoping your opponent doesn't see your threats (and making mediocre moves that threaten something for that reason) is something that is characteristic of only total beginners, whereas not considering the opponent's checks, captures and threats is a problem that affects players well into intermediate levels.

My opinion is tactic's is what to improve on. Tactics are common to everyone's games, and all parts of chess. How you go about putting it all together is where everyone is different. Books, videos, lessons, looking over games. Realistic goals are needed. A thinking process to get from opening to middle and ending, I think GM Silman has as good as any. Igor Khmelnitsky book is another way of training too.  When dealing with coaches, they usually try to get you to buy into their thinking process. The amount of effort that is put into the game by players compared to the returns are pretty low I would suspect. Reasons everyone will have them for not getting better. To become a GM is compared to the money and time spent on a 2 yr deg program. So to find the correct coach that can get you through to that level of play is going to be up to your pocket book and find the right person to form your game to get the most of your time and money. Deg programs are one size fits all, pass and fail. Different results will be with chess mentoring due to one size doesn't fit all.  Good luck. I am still trying to short cut my way to A class player.

The end game