well at first i would like to say that most problems or injuries caused in bodybuilding for beginners is mostly because of the wrong technique they do beside they carry heavier weights thinking that will help them increase their muscle mass .. most of common bodybuilding mistakes is centered on biceps and triceps workouts or back workouts !
people who complain that their arms don't grow fast or as they want well that maybe because they do the mistakes in this video

bodyvideoz.com/videos/265/common-mistakes-for-bicep-and-tricep-exercises

second when it becomes to back injuries most common mistakes in back working out

bodyvideoz.com/videos/188/top-muscle-building-mistakes