There should only be one rule when it comes to anal sex: she should try it at least once. Anal sex is kind of like beer. When she first tried it, she didn't like it. After a few more sips of some different brands, she starts to develop a taste for it. Once her taste buds start to tingle, she wants more of it. She's going to be beggin for it all of the time. So they suck your hard cock to get you hard and then beg you lube up their tight brown holes for some hard anal penetration. Don't just shove it right in there, though. Take your time. Like drinking beer, if you drink too much too fast you're not going to want to drink it for a while after that.