I read something at alaska bowhunter dot com which sounds good; though I still haven't tried it. Google alaska bowhunter.
start with a low brace height, fix a point and mark the height the of the hits. Twist the string 5 times and use the same fixed point. if the arrows land higher, and the bow sounds quieter, it's getting better. after one of the twists and the arrows are landing lower, you've reached a brace height that is too high, so take the twists back off.
when you think it's 'right' test it with a fletchless arrow.