start on a small ones. and practice lots. i aint a freestyle jumper but i can jump a bit. for what its worth heres my tips, stand up with enough speed to clear the jump be in a good attack position elbows out knees bent. the throttle control will effect the attitude of the bike in the air - shutting the throttle off in the air will drop the front wheel [nose dive]this can also be done with the back brake - opening the throttle up will drop the back wheel [ its handy to be able to remember these if things go a bit pear shapped while ur in the air] if it does go a bit haywire dont bail off, its best to have suspension and a foam seat inbetween you and the ground. remember to have a little gas on as u land or you will discover the joys of engine braking. by crunching your nuts on the tank and kissing the front mudguard [ unless ofcourse you like that kinda thing ] get good at the basics first and just build up slowly,,,best of luck IMHO tho the best advice tho is ''buy some good knee braces''