I fold it, sort of like it comes when you buy it new--but smaller,then I put it inside a plastic bag (the kind the newspaers come in). The plastic keeps the wrinkles out (just like when you get a shirt cleaned, it comes back in a plastic bag). I also fold it just before I leave in the morning, and hang it up as soon as I can in the locker room where I shower and change. It is in the bag max of an hour and a half. I have no problems with wrinkles. I had a trunk bag, and could put three shirts in it vertically, along with underwear and socks... I keep pants and shoes and coats at work.
My current bag is a large camelback style backpack, and the clothes fits inside nicely--no wrinkles.
train safe-