My skateboard tend to steer to one side. what can i do to fix this?

im guessing it involves tightening something to level it out. but im unsure of which screw or what. please be specific. :)
Answers:    loosen the bolt on the bushings of your board they are the little rubber ring things.
ok turn your sktebord upside down ... you see that nice big bolt on your truck ....TIGHTEN THT DEVIL UP BOY!!!!!!!!!!! the one just higher than your trucks