These 3 most-performed chest exercises can give you lots of muscular benefits or joint problems if you do not follow the right instruction.
the first and the most important instruction is actually to avoid barbells! the barbell takes your freedom of range of motion and flexibility away which can limit growth and restrict mind-muscle connection and worse than that, cause impingement and injury.
The second is to make sure you have a good thoracic extension, in other words, make sure you do not curve your upper back which can limit the range of motion and cause more injuries but do not overextend it as well.
third, make sure you do not bend the wrist backward.
forth, do not put your thumb back.
fifth, do not go too wide or too narrow.
sixth, arch your back a little bit for better stability but do not arch too much.
seven, bring the bar between your nipple and clavicle(collarbone).
eight, do not do declined variation! it forces your shoulder into too much internal rotation which can cause lots of injuries.
nine, spread your feet so you have more stability.
and ten, do not bring the bar too much down or too much up. make sure your elbow is always bent to some degree and avoid locking it and also do not bring the bar all the way to your chest and make sure you do not go lower than one inch to your chest.