You sign up and show up with your car pretty much empty. Pump up your tires about 5-10 pounds higher than street (use chalk to make sure you are not rolling them over) then go out and have fun.
also check out
http://www.tirerack.com/features/solo2/handbook.htmIf the one this saturday is close enough sign up today for it and get there early. Look for my red miata with the tires hanging behind it. If you dont sign up it looks like you can still run no problem just show up early.
if that one is to far how about atco raceway on the 23rd? I'll be there also.
http://www.myautoevents.com/pls/mae/frmEventDetail.Show?psevent_id=2962