Take home messages: Be clean, Have plenty of lubrication, relax, and make sure your partner takes it slow as you are starting out.
Follow up: Hair is fine and you don't need to shave it. Just make sure the hair is not extremely dirty. (Which it's probably not). You should try to go to the bathroom first definitely. That is because something will be going inside your anal canal. If feces is already there, the object (penis) could hit it.. So at least try going, if you don't have to go.. then you should be fine. (personal experience) As far as cleaning, usually just water to "rinse out" the inside. I would not suggest using soap or anything like that. It could sting and may not be made for the inside of the body. Just a brief rinsing should be enough. You don't have to like scrub or get all the way inside. Just a finger should be fine. You should probably do all this before he comes over. You don't have to do it all like right before the act (unless you want to). The point is to just try to eliminate any feces before and then rinse out.
I have done that and have never had any problems.
Also.. sometimes anal sex first feels like you have to go to the bathroom. But don't worry. If you already went to the bathroom or tried to and didn't have to, nothing will come out. It just feels that way.