What common things make weaker players weaker in your experience?

I'm ~FIDE 1400. I am commenting on players around 1000-1150 FIDE. In India, these players are usually quite strong. They play good moves and all, till the time they see thay their opponent is playing *normal* moves. As soon as you play an unorthodox move, they stumble and start making errors. In a recent tournament, my 1120 FIDE opponent was outplaying me and we entered the late middlegame with a good advantage for my opponent. Then, as soon as I played unorthodox moves like Kh8, g5, h5, etc., even after he had played f4 before this, he started making errors. Grave errors. He allowed me to enter an endgame with a definite edge for me, which I converted.

Too much talk

Like GOP says maybe not so useful, but here are some thoughts that come to mind.

Generally I'd say the stronger a player is the more tension they can handle.

There was a joke among some masters at a club I used to visit that no player U2200 could resist relieving pawn tension (leaving two pawns attacking eachother) for as many as 3 moves.

Along with captures I'd say the lower the rating the less aware they are of all the transitions. As an easy example lets say we have a R+R+N vs R+R+B position. Lower rated players are likely to rush to one of the endgames (rook or minor piece). Stronger players may trade only one set and play for a while in the R+B vs R+N, and even stronger players (if it's useful for the position) may not trade at all.

Another. I think the lower the rating the less aware they are of practical chances. Especially new players will only think what the engine tells them (I don't blame them) but eventually you realize 0.00 may be extremely far from a draw, and 2.00 may be drawish. It just depends.

So accordingly you choose your opening and middlegame play from this.

For example it's common to hear a low rated player want to avoid the 4 knights, or a d3 Ruy because it's "boring" and "drawish" but a strong player will happily give you 0.00 on move 15 in a complex position because in practical play there's a lot of potential to outplay your opponent.

Another. The stronger the player the more they'll fight in the endgame. Plenty of times I've had a "drawn" endgame against a 2200+ OTB, but I get outplayed and lose. Plenty of times I've had a "drawn" endgame against 1800 players OTB but I win...

And some of them really are "dead" draws, but you find ways to force accuracy, and then wait for them to be inaccurate.

There are also ways to use the clock.

I'm probably still a novice at this stuff, but one game that comes to mind is a game where I screwed up, and now I'm faced with a middlegame where my opponent has all the play, and it's a big kingside push against my king

So a "normal" reaction is to find some desperate counterplay somewhere else. Rush out a pawn break even if it's a sac, and try to make a mess.

But I decided the problem was there was too much time on the clocks. Either way I was lost, so I decided not to go for desperate play until my opponent had less time. I curled up into a little passive ball on the kingside and let him burn time. Then I saced a piece in the center to make a big mess... and I ended up winning.

Maybe a casual observer would think I was an idiot and got lucky, and in some sense that's true, but there are a lot of practical decisions like this... and of course you can also use this when winning. If you're in control of all the play in a position, sometimes it's useful to alternate a lot of threats but never execute them. Then after your opponent burns time you can initiate the critical position(s).

Haha, I guess so.

It's like after they both decline once, they both decide to never calculate it again

Leaving aside the lack of precision due to bad form, which can happen at any level, the question should be if the player understands what's happening and if he's capable of playing accordingly, thus establishing the sources and not the consequences.

On the way around, trying to categorize the mistakes according to the current competitive strength of a player can be deceptive. For instance, a number of players work on pattern recognition on some systems and become pretty good at them, but when taken from familiar waters they don't know what to do. Others are talented but lack the time or disposition to work hard. Then the same sort of "mistakes" can happen at different levels and for very different reasons.

Players rated below 1000 don't check whether their pieces are hanging before they make moves. Even players as good as 1400 have the temptation to play empty one move attacking moves which can easily be paired. I am talking about chess.com ratings, I am rated 1911 rapid, 1853 blitz as of the time of writing this comment.

I follow you on quora, I like your analyses and responses there.

Thanks

I am a weak player myself at 200 something in rapid

Blunders happen all the time. 

Some players fall for the Scholar's mate, including myself many times until i learnt how to defend it and do it myself. 

People would often sacrifice a bishop for a knight, sometimes even castle for knight.

Body language can give away a LOT, especially with newer players.

Saying a position is a draw, when it is a draw, and offering a draw, when there is still play left in the board.

First, trading everything,one mover (only cares about that one move, don't calculate the problems that can come with it,and last not enough knowledge on puzzles, matting patterns, openings , middle game and end game

Moving impulsively, without considering the opponent's likely replies.

Attempting to attack with one or two pieces, instead of developing more pieces first.

Ruining their own position (especially their Pawn structure) with a series of one-move threats that come to nothing.

They rely too much on calculation and not much on general principles, a strong player can play a reasonably good game without calculation just relying on principles of solid positional play , weak players calculate too much , mostly inferior risky moves which an experienced players rejects without even considering, thats one thing weaker players should try and cure , a good filter in move selection

Fischer once said, "Patzer sees a check, patzer gives a check". Tal, however, joked "If you see check, give that check. You never know; it might be checkmate!"

I generally find that most weak players do not review their games, they prefer to learn the hard way - by playing a million games and hoping to grow in the process, it works but its a very slow way of improving. At some point we hit a wall and have to review our mistakes and most bad players avoid this.

Chess is not poker. Body language doesn't matter. I play the board, not the opponent. You can read my body language perfectly, I don't care, I care about playing well enough so that you can't beat me (and hopefully so that I can beat you) no matter how much you read me.

A defensive and timid approach to the game, the beginner rabbits must attack if they want to become eagles and not afraid to sacrifice pawn and pieces in the opening

Congratulations! I see that you have improved a lot and that now you are 600. There is a big difference between 200 and 600 in my opinion.