I've received some version of this question several times so I've decided to just post a little blog to put it out there and so I can easily link it. ;c)
Dear Anal Angel,
I would really like to try anal but I'm unsure how my significant other would react. How can I convince her to try it and, should it get that far, do you have any tips on making it the best experience possible?
You are very right to be concerned! A lot of women are anti-anal because of bad first experiences.
In my case, I was into it and it was my idea to try it. But that doesn't mean I haven't had my own bad experiences which have made me question whether it was something I really wanted to do again.
My advice first for approaching her would be to go cautiously. Have you two talked about it at all? Maybe not in the context of your relationship but rather in a more hypothetical way which might seem less threatening? Show her amateur vids (amateur would be a must because pro is too fake) where a girl is enjoying a cock in her ass. Or if she isn't into vids, whatever her favorite medium might be. If nothing else, maybe just go with facts such as the anus has the most nerve endings in one spot other than her clit. And doesn't it feel good when you play with her clit?
If discussion is out of the question for some reason, or along with the discussion, try slipping in a little anal play.... pun intended. ;c) While going down on her, fucking her, whatever you two happen to enjoy most, rub her anus without inserting. Just give her a chance to realize how good it can feel when done right. If there is no protest, then maybe you can try pushing it a little farther. Again, pun intended.
Which brings me to some of my most important advice. There are three things which matter most in anal play of any kind: Lubrication, lubrication, lubrication. I cannot stress enough how important that you have some form of lube. Spit or her natural lube does work but you will need to be much more mindful of it as it is not quite as slippery and goes dry unlike most synthetic lube. The other thing I would stress is angle. It can be difficult to be sure about what angle is going to be most comfortable for her but if you take your time and, again, have plenty of lube, you should be able to find the right angle. Personally, I like to be on my knees with my legs tucked up under me a bit. As opposed to spread and ass high in the air as I would for doggystyle. I find it gives a much smoother entry.
Also from my own experiences, I find that if it gets painful, pulling out and trying again actually works far better than playing the waiting game to see if it goes away. I can't promise it is the same for her but something you might keep in mind.