The keys to singles are consistency, shot selection, and court positioning. First of all, you need to stay consistent. Do not go for a winner down the line when your opponent hits a sharp cross court angle; instead you should go for a looping, topspin forehand back deep cross court into the corner, enabling yourself to get back in to rally position. Do not force shots you know you can not hit, and I will go to this in detail with shot selection.
Many times you can hear a coach or pro commentator refer to singles as a cross court game. This is because the cross court shot is the most consistent shot, which branches from the most important key to singles. If a shot is a 75% rally ball hit cross court, it will be hard to change direction on that ball. Not to mention, you will have to go over the high part of the net and you will have less court to hit in to. The cross court net is approximately 6" lower at the middle when compared to the net down the line. The cross court shot also enables you about 10-15 feet more margin for error because the cross court shot goes longer. Hit a 75% rally ball back cross court until your opponent gives up a short ball, in which you should either go inside out or down the line most of the time, and cover the line you approached down on. You should you have only been playing for a year, but you should strive to make all your winners at the net, at the approach shot, or win off your opponents unforced error.
The last important idea is court placement. I am not an expert on this so I won't be able to give you much guidance on this topic, but I know it is important. The main key is during a cross court rally, you stand midway between the middle of the court and the singles sideline closest to where the cross court ball was hit. You are anticipating the cross court shot because it is most likely where your opponent will hit the ball. This makes you run less, and makes your opponent make more errors because if he doesn't hit it back cross court, he will either hit a down the line shot which you can get to (50% of the time), miss a down the line shot going for the winner (35% of the time) or hit a winner (15% chance of the time). Those are good odds in favor of you. Search Wardlaw directionals for more information on this topic.
Good luck to you in your tournament as well.