"If you shoot with fixed sights from 15ft up or more, are there any particular techniques you use to improve accuracy?
Does your practice shooting from a ground level postion hinder your accuracy when you are 15ft. up or higher, especially at deer coming close under your stand? "
Best to practice it before it happens. If you know the tree and surroundings you'll be hunting from, simulate the shots over and over before the season begins. Plenty of time.
I've used a Keller site before (years ago) it was good. Like the mulitpule pins now. 15' is almost like being on the ground. Above 20 has some affects on placement. Under the stand is not a good shot to take with a bow, but if you have too your form is the most important concideration. Practice again is a good idea. Shot placement is critical and small and the feeling that you can't possibly screw up the shot is strong and not what the mind should be thinking.
If trees arenot avalable, practising from the roof is good and some optics are always helpful.