Now I am by no means a pro or even competitive park rat but today I invented a great way of excersizing in preparation for the jumps and jibs.
All you need is a floor, two couch cushions, and a bunch of empty space.
Its really simple actually, place the cushions apart form each other (whatever distance you desire) and start hopping back and forth trying to land nicely balanced in the very center of the cushion. Then start varying your jumps by throwing in some spins and grabs.
Its similar to tramp excersizes but with the added difficulty of having to aim at a desired landing zone, and the fact that you are trying to leap off of thick shock absorbing cushions really works your jumping muscles HARRRRD!