Speaking strichtly from proctology exams ... the trick is to not clinch and relax. the asshole is designed to clinch learn to relax and breath ...
As a past anal groomer ... choose shorter, small diameter, straght dicks to start - the various curved varieties can poke the sides which is painful. Also just as every vagina has a different depth so to the anal canal. the shorter the lady the shorter the dick she can accomidate BUT the is not always true. Learn your limits and go slow ... you need to discover how long a dick you can accomidate because that wont likely change much. The diameter of penis you can take because it will not change much, but you can stretch the rectum over time by sizing up. OR, You can train the rectum - which is painful - to accomidatre much larger sizes which entails large insertions that rip and tear the rectum and can cause bleeding and infections but the rectum each time it is damaged will heal to accomidate larger diameters. (i call this the bite the bullet approach) I recommend learning your limits and sticking to them every woman is different but typically smaller women smaller dicks ... larger women larger dicks - or should i say longer.
The pain typically associated with anal comes from too deep - much like poking the cevervex can be for tranditional sex, too thick - a dick strenching and tearing the rectum much like passing an extremely large turd, lack of lubrication much like passing an exceedingly hard dry turd, and poor positioning not providing a straight path.
Go slow, there is actually a device (see amazon: Lube shooter) you can buy that allows you to insert lub deep in the rectum dont just lube the rectum but 6 to 8 inches inside. (use silcon base lub - lasts the longest - DO NOT USE SILCON RUBBER TOYS WITH SILCON LUBE IT CAN DISSOVLE TOYS ). Water based lubs dry and then you have a painful gripping effect that will totally suck. Once the penis is inserted sit and hold allowing the asshole to stretch and relax before moving. Learn which positions give the dick the least impedided access and then relax and breath and dont clinch. It is my understanding that the fun is once you learn to relax and what position works and how much lub to use when and where ... you need to learn to relax on the trust into the rectum and then clinch on the withdraw stroke. The clinching provides the stimulating effect most women enjoy about anal; however, timing is everything because clinching on the thrust is where some of the pain comes in as the oraface is designed for out and not in. Properly taught most women enjoy anal to some degree as there are many nerve endings - most of the people that really enjoy it are turned on to a certain extent by the idea of anything "taboo". The bad girl, bad boy feeling seems to hieghten the pleasure, so if you are into other types of taboo ... you will very likely properly trained enjoy anal as much as vaganial ... i have even ment a few that enjoy it more. good luck with it and relax and enjoy
I'm guessing this may be for a sig. other of boyfriend, then will move to the hobby.
I firmly suggest finding a person with a little dick and no balls. Let me think, OK, I've got it..........I suggest either deerhunter or wakeup as they both fit that criteria.