when i got my heli i sat on the couch and took it up around 3ft and waited for it to drift in a direction and set her down and adjusted the trim a little away from that direction and took her back up and repeated that trial and error untill the bird was as near stable and hovering in one spot with the least drift.

the heli will never just hover in one spot. It will always drift one direction or another but u want to get it trimmed as close to stable as posable so u don't have to fight the heli from always going in one direction all the time.