What's the fastest way to get better?

Best way is to know yourself. Go over all your losses and find out why you lost. A loss means there is a weakness you need to eliminate. Once you do that your game will improve.

Tactics is not just used for attack but for defense as well. If you can see a multiple-move trap ahead of time, then you can avoid it.

get a chess coach

If you want spend some minutes reading here http://www.chess.com/forum/view/general/improvement-in-chess-according-to-elo

don't be on the horse

Always play with people who play better than you. It helped me improve my rating.

Once you master the fundamentals of chess and the endgame in a systematic and very thorough manner (like boot camp in the military) then you begin the real work and sit down alone at a chess board and play over IM and GM games (alot of them) you cover up the GM's move with a book mark or hockey card write a move down the move you think he played on a piece of paper uncover his move see what he played and compare why and what for? if your moves aren't the same as your job is to figure the reason why they are different Chess as David Bronstien once said is a game of investigation. If you do this the right way for 4000-6000 games your thinking with have greater clarity your vision will be better and you'll see the chess board like they do.

Practice of course makes the player when you play it's best to pick your opponents wisely and carefully you want to avoid monkeys who play 1.e4 e5 2.Qh5 all the time and players who play in a very rushed way with no plan or aim from the start of a game bad habits, no vision, bad thought process rush, rush, rush and bang pieces he's contagious stay away best player to practice with is your equal or better than you.