Try to cheat to be a little lower than the other plane at the merge, but already pulling up in your lead-turn as if you're just trying to get back to co-altitude. Don't go pure vertical, but bias it oblique a bit towards wherever the sun is to make it harder for the other guy to see. In the first part of the turn aim for 3-4 G's but back off on the G's a bit as you pass vertical so you don't pull it into a stall going over the top. If you float a vertical turn (immelman, loop, whatever), you'll gain lots of altitude but you'll have a huge turn circle and be slow/helpless at the top if the other guy went up too but turned inside you, and he may win with a vertical snap-shot as you float over the top.
When very very slow, don't be afraid of nudging the rudder a bit if you need the nose to go one way or another, but also be prepared to IMMEDIATELY apply opposite rudder and move the stick fwd a bit if the nose starts slicing, especially with the power still up. Power on spin entries can be violent so listen to what the IP says you can and can't do.
Don't try negative G maneuvers unless you like chewing second-hand banana.
Eat a little protein too in your pre-flight breakfast. Egg has worked good for me in my flying career.
Stay hydrated but not so much before flight that you have to pee before the flight is over. The last thing you do before you step out of the building to go fly is make one last bathroom stop. Seriously, don't pass up a chance to pee. Ever.
Watch getting the nose buried downhill. If you get going fast the instructor WILL intervene. If you try a split-S, make sure you're fairly slow to begin with and get on the pull early or you'll get going too fast and you'll either end up with a HUGE turn circle that the opponent can cut inside, or your IP will intervene.
Keep the ball centered if you're in a rate fight (level turn fight going 'round and 'round). Don't get greedy until you're SURE you can cash in any extra speed to get the other plane in your gunsight.
A rolling scissors is cool but often degenerates quickly into a flat scissors. If it keeps rolling, one or both planes will often go through the floor which ends the engagement.
Pull to the other guy's high-6.