i usually hang polos to avoid unsightly creases.
this is the rule of thumb i have:
1) shirts and light sweaters that are to be worn fitted, slim, snug against the body like a tshirt, (has a little elastane) etc., i will usually just fold. the stretch will make the creases disappear.
2) shirts and polos that are not to be worn slim, snug against the body, but a little looser, blousier fit, i will definitely hang.
3) heavy sweaters i fold
i dont use wire or narrow hangers. i have alot of wide wood hangers so i dont have any issues with indentations at the shoulder areas.