How do you dostunts on the game "kinetica" for ps2?

i realy want to know because it's saying stuff like "durng a ground stunt do the string of stunts that it says to do at the bottom of your HUD for extra boost (same thing for air tricks)" and "do stunts for boost" and all the crap, and i keep wondering "how the h*ll do you do stunts in the friggin' first place???????????" it's rally pissin' me off because i found chat codes telling m about stuff like if you complete a season this will happen or you'll unlock that and all that. know you have to hold down R1, but what else do you do? i've pressed R1 and then just pressed a couple of random ons and ended up doing a trick, but it only happened twice, and i see other computer players doing tricks in the air like off every jump and then just randomly doing them on the ground, but i just can't friggin' do it!!!!!!! can sum1 pleeeezze tell me how???????? pleeeeeeeeeezzze??????????