13 or 14, start of high school. I would actually put a small amount of effort into school, both HS and college, go to a different (and better) college, not go to law school, go into a different profession, bang more chicks and travel a lot. Not travelling is one of my biggest regrets of my late teens/early 20s. now that more chicks are "of loose morals", into lesbianism, three somes and partying it would seem to be more fun too.
Of course, I have a good life already with a great wife and family, so I wouldn't do it if I had the chance.