The trampoline is a wakeboarder's version of a flight simulator. It is more economical and usually less painful to get familiar with a rotation, a body position or a handle pass on a trampoline before taking it out on the water.
To get the most out of your trampoline time, try to simulate each trick as closely as possible by making sure you take off with the same stance and body position as you would on the water. This means getting your feet at the right angle, hips up, head up and taking your tricks up first.
Always lead your spins and flips with your head, and DON'T try anything beyond your ability. Tramps look like a lot of fun, and they are, but just fly off that sucker once and you will have a whole new respect for it. A net is a great idea. It will keep you from flying out and onto the ground. Instruction from a certified teacher at a gymnastics center will also help you improve much faster with less chance of injury.
Many wakeboarders tie a rope to a tree (or some other solid object) for obvious reasons. The rope gives you an axis to spin around and also gives you the ability to change direction mid-air. You can flip and spin with or without the rope. It's a good idea to do tricks both ways. Anything that involves motor skills will only enhance your kinesthetic sense.
If you've done everything right on land, all you will have to do is get the proper edge and pop off the wake, and your rotation should come a lot easier now that you've done it many times before on the trampoline.