There's tons of info on this all over the web... I seem to remember something like "The Complete Guide to Anal Sex (for couples" or something like the "Women's Guide to Anal Sex". Of course, like all info, don't just believe everything you read.. use your head (the big one).
Anal sex can be a wonderfully intimate and satisfying part of an adult relationship. However, you can cause significant discomfort (pain, actually, and potentially even injury to the rectal lining) if you go about it the wrong way (especially for a female partner new to the act). So: lube is a good idea, start with a small finger to get her used to the concept and only when she's good and ready move on to bigger things, don't be too agressive with insertion and thrusting especially if you're on the large side, go SLOWLY at first and pick up the pace only when and if you're sure she's ready, etc... Don't try to reinvent the wheel at first... i.e.: don't go for some acrobatic positions as some angles of entry can be very unpleasant feeling for her.... do what feels good... at first, this is usually her on her stomach with her rump in the air (a pillow under her belly helps) and you on top, entering slowly at a 'normal' angle of entry. Save the fancy shmancy stuff for later, when you're both used to it and ready.
OF COURSE, good hygeine (sp?) is crucial for this to be pleasant of course (as it is for ALL intimate acts IMHO) and to avoid/reduce the chance of unpleasantness, it's a good idea for her to make sure her bowels are completely empty before starting. IME, it's an understandable concern for some women... they don't want to have anything happen that will be distastefull to themselves or for their partner... thus, in addition to empty bowels, an enema beforehand is also a good idea, especially for those new to the act. Disposable Fleet enemas can be purchased at any drug store and they'll cost you less than a small box of condoms. If there is some unexpected unpleasantness, don't make a scene about it... it's not the end of the world... behave like an adult and a gentleman... help clean up if necessary and make sure she's not too freaked out by any mess... TALK with your partner and she'll love and appreciate you all the more for it. I'm not one for sexualizing elimination or waste products myself at all, but remember: on the rare chance that some makes an appearance, a little bit of **107** isn't going to kill anyone. With that said, if she uses the bathroom before hand, and opts for a quick enema or two, the chances of any such unpleasantness are just about nil.
Condoms never hurt either of course, and are a good idea in all relationships (unless of course you're totally monogamous, safe, committed, etc...). Most of all, when it comes to anal sex remember to TAKE IT EASY! Though muscular, the sphincter and rectum are not as elastic as a vagina, and of course they're not used to the sort of enthusiastic activity that often accompanies energetic lovemaking. As you should with ALL sexual acts, PAY ATTENTION to your partner and her reactions to your actions... believe me she'll let you know if it's not to her liking... and only an insensitive clod would ignore such warnings for his own pleasure. Such a fellow doesn't DESERVE the special gift that is his lover's anal cherry... and I'm sure you're not that kind of guy.
Also, don't forget: no 'double dipping' as it were... once you've inserted anything (a finger, a penis, whatever) in her pretty bottom, under no circumstances are you to put it back in her vagina without thoroughly washing it first... bacteria in the rectum WILL contribute to vaginal infections. And that A2M stuff (going directly from her ass to her mouth) is best left for porn actors IMHO, who get paid to do stuff that might later require a regimen of antibiotics. So, remember to keep it seperate and clean (it's ok to put a just-out-of-her-vagina finger/penis into the rectum w/o washing in terms of health issues... in fact, a little straight sex before moving onto anal initially can be a good idea to relax her, get her in the mood, etc... ).
Finally, if she's receptive during the act, don't forget to use your fingers in front for manual stimulation on/near the clitoris to aid her in achieving orgasm... you're BOTH supposed to have a good time of course .
I've been fortunate to participate in such activities with all but two of the women I've been sexually involved with. Of those, half weren't that crazy about it and thus it was a very infrequent element of our sex life, while the other half had a genuine enjoyment for it and would suggest it themselves w/o any prompting from me, as it clearly gave them pleasure and they KNEW I enjoyed it too. The sight and feel of such an intimate act so requiring of trust with someone you love is a very special experience.
A woman's ass is as much an exquisite thing of beauty as a well-formed bosom, and capable of providing an enormous degree of stimulation and pleasure. Anal sex isn't "better" than vaginal sex (or oral sex for that matter)... it's simply different (for both partners). And the occasional variance from the status quo helps keep long-term physical relationships fresh and enjoyable for everyone involved.
Do some more reading (or speak to someone about it if you have access to such a person) and if you're both willing, go ahead and give it a slow and carefull try.
Good luck and enjoy. (pretend there's an animated anal sex smiley here)
