When it comes to undressing, shoes are always off first. Otherwise, it could be either top or bottom off first, with not real preference so long as everything is coming off at roughly the same time.
If any clothing is to stay on, it would be bottoms off and a tshirt on. Although now that I'm thinking about it, when I shed clothing at friend's, while more often than not I'd keep a tshirt on, there have been times when I'd be topless with either boxers or a sarong covering my groin ^_^