The 360 is the air everyone wants to learn. It's fun, and it's not as hard to do as it might seem.
First of all, find a good little jump that doesn't throw you more than two feet high or 12 feet in distance, and preferably has a smooth, flat area to land on. That's all you need; most skiers take too much air when trying to learn the 360.
Twin-tip skis make learning 360s much easier because they allow you to learn in stages. First you want to jump into the air and rotate 180 degrees. Start the rotation by twisting your shoulders and hips as you leave the jump.
Once you're getting to 180 degrees without difficulty, it's time to go for the full 360. Take a little more speed, start your rotation with a little bit more force, and most important, turn your head in the direction of the spin to help the rotation. Make sure you keep your head and eyes up so that you stay on axis.
When you've got the feeling on small jumps, gradually work up to bigger and bigger jumps. Repetition is key. This is one move that requires lots of practice.