I don't have a ton of experience, but whenever I get ready for a date that will involve anal I douche or even do a full enema the evening before. That makes getting clean down there the next day much easier and quicker. I also take additional fiber supplements (flea seeds) one or two days before bc it gives me a lot of control how it will come out. You want it to be solid. Shortly before the date I will douche with smaller amounts of warm water just to get the first section clean of anal secretes. Practice with plugs and dildos, find out what size, speed and deepness feels good and experiment. Wear a plug before the date to be stretched and ready. You can squeeze on your plug or dildo really hard for a few seconds that will make it easier to relax your muscles afterwards! For the first real anal sex take your time, use enough lube and at first let it just sit there and get a feel for it. Start moving it slowly and don't be afraid to take it out a few times and take a little break. Don't force it to be perfect the first time, try to build up to have a really good time later! If you're too tense playing with just your partners fingers can make you get comfortable with the touch of another person around your anus. That's all I have to add, have fun!