Interesting thread Soul. I actually do have a teenage girl so its very topical ATM!!!
Dyeing hair- she has had foils a couple of times since she was 14 and now has it nearly all a couple of shades lighter but i insisted she pay for it and that it was done by a hairdresser.
Shaving I insisted she start waxing her legs not shaving and she is now grateful as she has quite fine hair and does it herself or uses her epilady. She shaves under her arms though.
Piercings She got her ears done at 8 and DH did the top of her ear a few months ago when she wanted it done. Interestingly he said no to belly button whereas I wouldn't have minded.
Drinking I don't encourage this and she seems t be the one at parties looking after her drunken friends which seems to have put her off. We have let her have a cruiser at new years when she was 14/15.
Smoking I would never let her and she is still fairly anti, I am an ex smoker so am more anti smoking than non smokers I think LOL
Swearing trying to stomp on that one ATM!
Going out at night we do let her but we have to know where she is going and who with etc before we let her. We don't let her go to parties where there will be no adults. She has a boyfriend so she often goes out with him but usually to his house.
getting in the car with friends This is really tough when it comes to the crunch!! We said no to anyone on their Ps driving her but she does have a couple of sensible friends we trust and her BF who both we and his parents have spoken to about safe driving but its still scary.