For a very general question, I think you got a lot of good responses here, as there are so many variables to climbing. I'm no guru but here are my humble tips. First, always check, check and triple check where your lines are and where you are working, and don't forget to look up frequently, as it keeps you in tune with your process. Golden rule, always make sure you are tied on with two separate lines before you start the saw-EVERY TIME. It can seem tedious, but just ask Jeff Jepson about his fall when his glove got stuck in the throttle and he cut his single flipline and fell to the ground. This sounds crazy, but I talk to myself in the tree, about my process, what is tied, what is not and my plan (go ahead, laugh, but it is effective). This makes sure your awareness is acute. Try to identify a person you respect in the business, and who has been around for awhile, and pick their brain about various situations every chance you get. Books help, but experience is worth way more. Last, start with small lower risk jobs/trees first, and work your way up. Have fun and be diligence with your process on each job.