The best advice I ever got was to practice 180s first. Try landing it backwards first, then try skiing backwards and landing forward. Once you have mastered this ease into 360s by going at angle so maybe you only need to do 300 or 320.
360's are fun because you can practice them at home (if you have snow and just a little hill). Remember a 360 is a twist and most of the energy for the twist is in your upper body-lead with your head and use your arms and shoulders to help throw the twist. pick a visual down the hill for your head to come back around to as a reference. You can cheat a bit in the begining by hititing the jump at an angle so you do not need to rotate so much to land it. You will not need much air. A 360 is a bit of a psychological hump-once you have done one they get easier. You can practice a bit on dry land by jumping and twistng a 360 in your sneakers. Try to keep your upper body in a line.