Well blatantly practise, crates helped me alot. Try and bend your legs as much as possible on takeoff, and throw yourself forward towards the bars, it helps to be more comfortable on the back wheel. When youre about to land push your legs out as much as possible but try and keep your arms closer to the bars, it means your weight will be more towards the front of the bike so youll be able to case it moreso but still pull it off.