Great fun, isn't it? The etiquette seems to be that if you tip in towards each other, you're on. The important thing is to keep the other guy visible. Depending on your aircraft type, you can either climb or dive away to disengage, or fly straight and level. Loops etc are of lttle use in dogfights as you lose sight of your antagonist, and lose speed. You could try a high or a low yo-yo if your turning circles and/or speeds don't match up well (high yo-yo: pull up and wingover back down onto his tail. Low yo-yo, dive and zoom up). Otherwise, just clench your stomach muscles, roll on 85 degrees of bank, and pull like mad.
Done responsibly, there's no harm in this. Obviously look out well for other aircraft in the area.
PS: Wide-Body can describe his patented technique for shooting down Nangchangs in a Rallye. Pop those slats!
PPS: What are you flying and where from? Fancy a contest some day near North Weald or Waltham?