I am an intermediate chess player (1500-1600 skill level USCF) and will enter the Open section of a State tournament. I would like to prepare for this tournament in three months, what would be the best way to become a stronger chess player to at least survive against 2000 USCF rated players or higher?
I think this question is a bit too broad to answer, but I'll give it a shot anyway. I think the best thing you can do in 3 months is to play as much as you can. You can play online and pick a semi-serious time control such as G/15. For all the games you lose (or really all of your games), you should analyze it thoroughly until you understand what it is that you could have done better. You can use a chess engine to help you as well as any other resource (Analyze the games with a high rated friend afterwards). If you played a poor move in an opening, you need to make sure you revise your repertoire. If you made a tactical blunder you need to ask yourself why you made that mistake and how you can avoid it next time, if you lost in an endgame maybe research that endgame to see how you can play better next time. I would suggest, at least, 5 games a day if you can manage.
There's not much you can do in 3 months, but the best thing you can do is play as much as you can and learn as much as you can from your losses. It is easy to lose and simply play another game and forget it happened. It is better to figure out why you lost and try to figure out how to avoid it next time.
If you could average 5 games a day, that's 450 games in 3 months. If you've learned anything from each of these games, that's got to be worth something.