The way I've always learned, it's highly frowned upon to grab a tshirt in a street fight for any kind of hold because tshirts just rip too easily. Any kind of joint manipulation that doesn't require grabbing cloth is cool-- americanas, arm bars, knee bars, ankle locks, that kind of thing. As far as chokes go, don't even try to grab a tshirt to apply a choke, you're wasting your energy. Anything where you grab your own wrists or theirs is better. Oh, triangles are good too.