I've got some pretty good experience, although only with women. I would say the first step is definitely for them to be as relaxed as possible. In order for that to happen, there needs to be some mutual trust and or understanding of what is going to happen, especially if it's the reciever's first time. They need to know that youre not just gonna slam it in there and rip em a new one...which you can do quite literally. It's very easy to injure your partner when engaging in anal sex...more so if they are nervous or uneasy about doing it. Foreplay and being very comfortable with performing the act yourself as the one doing the penetration is very important as well. If you seem like you know what YOU are doing that helps put them more at ease and makes things a lot easier for both of you.
Foreplay can be as simple as kissing, and heavy petting. Anal play with one finger, starting with just playing on the outside of the anus to get them comfortable with the feeling of someone doing so is good. You can use spit as a lube for finger insertion. Or vaginal fluid if we're talking about a woman, assuming youre engaging in foreplay like you should be and taking your time to get her plenty aroused. Only move from vagina to anus and NOT back from anus to vagina! The more aroused THEY are, the more relaxed they will be. Guys, make sure your damned finger nails are trimmed, you dont have any hangnails, and your hands are clean! Last thing you wanna do is cut your partner with a snaggly fingernail and or give them an infection in that area. Do something stupid like that, and you'll probably never get near that spot again!!
DONT RUSH INTO IT!!! If you guys are pressed for time, dont even bother. First time anal sex is not something to take lightly for most people. You both need to plan for it in advance. It's usually new territory. For most people, the anus has always been "exit only" and this is a totally new, and usually to some degree, uncomfortable experience. It does not have to be uncomfortable though. Anal sex is VERY pleasurable and can lead to "new", much more intense orgasms for either sex whether on the giving or taking end.....when done properly. Many people whether they have had anal sex or not, relate anal sex only to pain. This is usually due to some asshole (pun intended ) rushing into it with them, or because they heard from a friend that it hurt. "Oh my gawd, my man and I had anal sex last night....damn I'll never do that again! It was SOOOO painful!!" Thats usually enough to deter most with closed minds.
Lots of lube. That's the next most important thing. The anus does not self lubricate like the vagina. Many people do not understand that. I've found K-Y Jelly...the JELLY not the thinner liquid is best for anal. You want the jelly because it's thick. Thicker lubes work better. Think engine oils guys. What lubricates engines better? Right, thicker oil. You want to apply some to both your penis, and their anus externally and with a finger or two internally. Again, finger play is a good thing. Towels are also a good thing to have near by. Preferably towels you dont mind getting dirty. Or towels you can bleach if you need to. Anal sex is actually usually pretty clean provided your partner is clean before hand. If they have made a bowel movement recently or need to before the act, there's more chance of it being a little messier but, still it should be fairly clean. A liquid enema to clean them out followed by a bath or shower ....both of you showering together and engaging in foreplay is a good idea. Back to lubes for a second. You do not want to use petroleum based lubes like vaseline or baby oil or similar. Reason is, they can cause infections. Especially YEAST infections in women if any moves from the anus area to the vagina during sex....which can happen.
Penetration. When it actually comes time to start trying penetration, you need to again, take your time. That cannot be emphasized enough!! Play with the outer anus with your fingers and penis head or glans for a few minutes. Slowly work the glans in and leave it there for a minute. Ask how theyre doing. Dont ask if it hurts! That will only encourage the idea in their mind that it's gonna hurt...which it should not if you take your time...but the mind is a powerful thing. If they are suddenly convinced it's gonna hurt, forget it. That anus is gonna clench shut faster than a pit bull's jaw and you will NOT get in no matter how much sweet talk you use.....usually. Slowly move a little more of your penis in. Slowly! Hold it there. Back out a little bit, then move a little farther in. Again, hold it there. What youre doing is giving the anus muscles time to relax. The anus in most cases is only used to having things come out of it. If everything goes well, I'd say within 10 minutes you should be in there. That does not mean youre ready to start pounding away though. Maybe after a few times but not the first time you have anal sex. Take it slow. SLOW strokes. Ask how theyre doing...not if it hurts. Tell them how good it feels...how good they feel...how sexy they are...how sexy their ass is...etc, etc. It's all about putting them at ease and making THEM comfortable. If we're talking about a woman, play with her vagina, or clit.
Seems like comon sense, but do not go from anus to vagina if you are doing this with a woman. Even if she encourages you to do so...she should understand anyway as a woman that this could give her a yeast infection or worse. Then again, some women know more about their bodies than others....so, it's YOUR job as the one doing the "dirty work" to know better. At least take a quick break and clean your penis off before having vaginal sex after anal.
I've covered everything I can think of. Relax, lube, foreplay, and take your time. That's pretty much it. The "A-List" to good anal sex. No matter your size, you should be able to engage in it with the proper steps taken.
Nice job still, although I'll never get my g/f to want to do anal. I've talked about it and she gets kinda offended. To make matters worse her best friend tried it one time and she told her it hurt like hell.