Dan Guthrie wrote:
I've only been doing this for 14 months but all my injuries were from doing something incorrectly. It took me 8 months to do forward rolls without driving my shoulder into the mat....roll - on eggshells for the first 6 months.
What he said.
By far the most injuries to beginners that I've seen have been to the shoulders incurred during forward rolls. Several of the individuals were overweight and middle-aged.
Some instructors push folks to do forward rolls from standing the first day. Don't let them do it to you.
If an instructor puts you into a randori--multiple attack practice--maintain your head. It's real easy to get carried away with all the motion and limbs flying and ignore your relative incapacities. I've seen beginners put in this position from "an old school" teacher and get hurt.
Other than that, follow/solicit tutoring on how to falls from your teacher and seniors.