If you're interested in training for longevity and injury prevention (which is my philosophy with tricking):
Step 1) Find a gymnastics gym. If there are no coaches available/look for someone who knows what they're doing.
Step 2) Use that coach/friend for advice, progressions, and SPOTTING.
Step 3) Build up to things. Drill it into the foam pit until you have it 100% of the time. Then drill it on the Tumble Trax, then into a big mat, then a smaller mat, and finally on the floor. At the beginning of each new progression, use a spotter. If you ever lose it somewhere, just go back a step.
Step 4) Be patient. It took me 3 years to get my backtucks to the point where I'm comfortable throwing them anywhere, anytime. Side summis took me 6 months to learn, and then another 8 months to learn right. If you are patient, there is a lot less chance of you getting hurt.
Or just go find something really tall and jump off and you'll have plenty of time to tuck. Whichever you want to go for.