GMs hang pieces; you'll never stop doing that. different situations on the board usually, yea, but a piece, all the same. :D
What does a 1600 rated player know?

The best advice I can give anyone is to work on improving practical playing skills, not gaining knowledge per se. I recommend Rowson's books (Chess for Zebras and Deadly Chess Sins) but I think this is the essence of his advice:
1. play games. Analyze them afterwards with opponent and other people especially strong players
2. take won positions and try to win them against computer
3. do chess solitare. Play over master games, but cover up moves and try to analyze and decide on best move
4. practice solving puzzles and problems
5. if you want to improve don't passively read chess books
He also talks a lot about psychology and here is more of his advice
1. Don't be perfectionistic
2. Don't let your ego enter the game (easier said than done, but he has alot of good advice on how to do this)
3. Try not to think that you ever have a won position. Dig in even harder when you have a good position
4. Be willing to grind and fight hard in even or slightly better positions
5. If you have a bad position try to change the character of the game if you can by giving up material, especially if you get the initiative
6. Don't panic when you have to defend; be willing to make defensive moves if necessary. Don't lash out if it is not warranted.

I found I got better when I started focusing on breaking chess down. The first question is how do you actually win a game of chess. Well, you win a game of chess when you are attacking the opponents king and he cannot relieve himself of the attack on his move. Next question pops up, how can the king relieve himself of an attack and how can I prevent it? The king can get out of check by moving to a safe square, blocking the attacking piece with one of his own, or by capturing the attacking piece. So from this point you'll set up simple endgames with a lone king against a king and a major piece, and practice the techniques of forcing checkmate. As you are doing these 'simple' exercises, you are learning technique. You will learn how different pieces can be powerful together and how you can limit the power of your opponents pieces. From these endgame studies with a few pieces, you will branch out, further and further back in the game. When you study middlegame, you will learn how certain structures may dictate a logic setup of pieces. The middlegame is very very rich in all of the different ways the pieces interact with each other. The thing to look for in the middlegame studies is for the different techniques that will help create a favorable inbalance in force so that you will be able to overpower the opposing king. As you get stronger, you will see more and more how the moves are part of a system, part of an ongoing struggle to overpower your opponent until you can overwhelm his king. Finally, you can study openings. Openings should not be concentrated on until you have built up a reasonable amount of ideas. Without keeping in mind how the pieces are battling each other, trying to overpower each other, any opening study will just be a waste of time. You can know an opening 10 moves deep in 20 different lines, but unless this knowledge has a connection to the 'why' behind the moves, it is completely useless. What the 1600 knows that the 1200 player doesn't is a deeper knowledge of the systems of chess, not just simplistic 'I move here and attack this' one move thoughts that beginners have.

Woodshover, somebody was "trash-talking" earlier, saying they could beat anyone here. So I set up a match for you(since they probably would have beat me). I told 'em you would crush them, and they didn't have any hope. I'm counting on you to back my words, woodshover, and show 'em who's boss!

That a 1200 rated player doesn't?
400 points worth of good stuff. (Geesh! The sorts of questions that are posted.)
sftac

Online I've had a player rated over 1800 allow mate in one,(he was beating me if he hadn't).
I'm pretty good at tactics I think, but for some reason I tend to miss pawn forks.
I'm rated about 1700 online on a different site.
Seems to me that a 1600 rated player has decent tactical ability, knows the main line openings at least 5-6 moves deep, and only occasionally blunders pieces/misses checkmates.

Some 1200's play very well and then some 1600's play like beginners, i think you will find that to be true on any site. But for the most part a 1600 is beyond hanging pieces and they start to drop 4 or 5 move combo's on people. They are at the threshold of becoming really strong players, a true 1200 generally will not display that kind of tactical ability and often fall victim to simple tactical motiffs.

I think the 1600 player doesn't hang pieces anymore, but the 1200 does.
I hover between 1500 and 1600. I still hang pieces sometimes.
Lots of ratings hang pieces. Though, there is a difference beween hanging a piece due to complete oversite, completely leaving the pieces en prise, and hanging a piece to an unseen tactic. 1600+ players rarely do the former but can still do that latter.

What does a 1600 rated player know...That a 1200 rated player doesn't?
I think there are 2 major things:
1. Never make the same mistake twice. Learn from your own mistakes, as well as your opponents. You can't go from 1200 to 1600 without making tons of mistakes in games (I sure have anyway :) ), but now I will very rarely get caught with a hanging piece / fork / discovered attack / etc.
2. Always have a plan. A 1200 player will usually just "make moves" for the sake of attacking or defending a piece. But a 1600 player is more subtle and usually has a long term plan and purpose for each move. If you don't have a plan... just make one up!
I went from a 1200 rating to 1600 rating (really slowly & gradually) & what I can tell you is a simple thing: don't repeat your mistakes & you'll always improve.



I went from a 1200 rating to 1600 rating (really slowly & gradually) & what I can tell you is a simple thing: don't repeat your mistakes & you'll always improve.
+ 1
The best advice.
I think the 1600 player doesn't hang pieces anymore, but the 1200 does.
I hover between 1500 and 1600. I still hang pieces sometimes.