Gym - weights, cardio, core strengthening
Places to practice jumps - Tramps, Water Ramps, foam pits, diving boards, gymnastics, etc.
similar sports - bmx, mountain biking, motocross, etc. Anything to get you comfortable in the air and going fast
Analyzing vids - checking how tricks are done, seeing what to look for in lines, getting psyched
Eating properly and sleeping well - Helps maintain focus and a fit body/mind. Important especially in comps
Thats all I can think of of the top of my head....