Some standard advice for newer combat flyers-
Don't hit the ground.
Don't maneuver when you cannot see the other plane.
Don't pull sudden maneuvers. Doing weird things makes it just that much harder for your opponent to keep clear of you
Practice flying eyes-off a lot. Do it until you can fly a four leaf clover that way and do figure eights both directions without watching the plane. You want to learn this so you can fly the match while keeping track of the other plane without worrying about yours. Flying behind your head and other tricks in a match is a good way to serve up cuts to your opponent.
Trim the plane so it doesn't do weird things. Get it straight. Get the tip weight and leadouts right. Adjust the balance point, control travel, and stab throw for a stable feel. The plane has to go where you point it, other wise getting cuts is mostly luck. For practice, trick up a special plane trimmed tail heavy and with too much elevator throw and practice flying that precisely. It will make a competition plane feel much easier to handle.
Eventually, you WILL hit what you look at. Flying for cuts, look only at the tip of the other guy's streamer. If you watch his plane you will hit it.
Do a lot of cloud flying. Try to hit a cloud from every direction(all eight ways) without watching your plane.
Learn how low you can be and still pull an outside loop.
As Ralph said, if you have a flying buddy, fly lots of practice matches. That means preplanning the match, talking about what you are doing/going to do, and practicing specific moves. When you just go out and tear up the sky you usually tear up some planes too.