There are a number of basic mistakes that bodybuilders make when trying to develop their muscles to their optimal levels. People shrug their shoulders instead of raising them up and down when perforing the shoulder shrug. They squat all the way down instead of just to 90 degrees and thus mess up their knees. All sorts of mistakes are made. Here is a link to a bunch of basic bodybuilding tips that should help most of us to get the most from our workouts.