-in a fighter, try to extend, then climb. If he is trying to set up a shot on you, break early, as his guns is only effective at close ranges.
-in a bomber, above 20k, if he is trying to climb up to you, hit the autoclimb. If he has alt on you, try to shallow dive towards your base.
Theese situations were the hardest to handle for me when i was flying a 262.