It really depends on the jump, but majority of them it's standing (of some sort) from start to finish.
James thats exactly what i mean, for 9/10 jumps you're almost ALWAYS standing up. I can never sit down i never have control over the bike like that. What i prefer to do is stand up and guide the bike with my knees tightened on the front fenders by the radiators. I remember one time i decided to sit down on one of our trail jumps... Flew forwards in mid air, landed on the rear shock and flipped over the bars. Thank god i still had the XR that time, it never quits running!