to add on to your good list i have only one,
"do not do anything that hurts you in the knees/joints/ect just because you think you have to or others have told you."
Ya, you have to be willing to experiment with variations and substitutes using criterions such as injury potential (joint/tendon strain) and effectiveness on the muscle. We're told to do a specific exercise and sometimes continue even when ineffective and injurious ie. BB bench press.
Much better to try other possibilities and stick with what works the muscle best (feel) and what doesn't hurt! I've been through that re: BB bench press, came to the same conclusion as Bob Chich and discarded BB benches. In that case, can try dumbbell presses, machine presses, weighted pushups or dips, or stick to fly motions.
The only grey area are exercises that are effective AND hard on the joints, in which case it's worth trying gentler but similar variations in form before discarding the exercise-dumbbells, cables or machines instead of BB, for example.
