The best way to prepare for a back flip is stretching. Get those muscles loose and ready to bend and than move onto a trampoline. A tramp will allow you to feel more comfortable doing a back flip and give you that extra spring the you need. Once you have that down start moving towards back handsprings on the ground. After that try doing a full on back flip on the ground.
I taught myself how to do them with three easy steps: 1.i got off my *** 2. I looked up a tutorial on youtube 3. And i tried it and now i can double backflip
If you are afraid to go back, don't do it without a professional that can properly spot you! I don't know if you're referring to a backhandspring or a back tuck but both are very different when it comes to technique. If you are trying to do a backhandspring be sure that your arms are strong enough to handle the weight you put on them. Do a couple of handstands first, jump, then catch yourself with your hands. When doing a backhandspring sit back as if your going to fall, swing your arms, stretch back in an arch position, catch yourself with your hands, and then rebound by pushing off your hands
Back tucks are a little different but if you're comfortable going back it's really not that hard. You basically swing your arms and squat back (not too far like a backhandspring) when your hands come up put them by your ears and jump up as far as you can. Be sure to have a good set. When you're in the air bring your knees to your stomach, pull with your hands to rotate, and then spot your landing.
Start with a deep pool. At least 8 ft.