Good technical tips from BSB, but let me add a couple things...
The pre-enema is a nice touch if the lady is anticipating anal sex. There is always a chance of coming out with a little something from last night's dinner
but for people with normal digestion (and reasonably high fiber in their diet) not much is stored in the rectum and spontaneous anal penetration is possible without any close encounters of the turd kind.
And it is, of course the rectum (not the colon) that receives the penis. Otherwise we would get messy!
BSB is correct that the rectum often needs to adjust to an object moving from the "wrong" direction and there can be some temporary discomfort (cramping) associated. The real hurdle (to use a poor metaphor) is the anal sphincter. Thats the little ring of muscle surrounding the anal orifice and it's whole
raison d'être is to keep that portal closed until stimulated by familiar pressure from
inside.
Lube is essential. The pre-insertion penis should be well coated but it's equally important to get lube inside -- the anus can be very tight and essentially wipe off most of the lube on initial penetration, so work it in with your fingers beforehand, or let her do that. (It's fun!) And once you're in, before you begin any to-and-fro, pull your fat belly out of the way and squirt some lube at the point of penetration. Then slowly begin a well-lubricated series of short penetrations (beginning with a slight "out") to move the material inside. If things don't get really slippery do it again. She'll thank you for that.
Working lube in with the fingers serves the second purpose of getting the sphincter accustomed to opening from outside pressure. A rule of thumb
is that if you can work 2 fingers around, your dick can get in next. Slipping in as the fingers come out can be an easy segue but requires some finesse.
Occasionally guys find that getting everything ready for the big trip leaves them less than dynamically erect. My advice in that case is to use something other than your dick. Anal penetration can require substantially more pressure than required to get in a wet vagina (which is 2-12/ lbs, incidentally). A good hard dick is a precise instrument and that's what you want. Half-flaccid may not get in or may pop out unexpectedly (both of which lead to the kind of intimate frustration we all like to avoid) or requires so much (poorly wielded) pressure that the operator loses control of the tool and damages the work area.
Finally, BSB alludes to the fact that there are no primary sex receptors in the rectum. That doesn't prevent some women from having intense orgasms from an ass fuck (I get tired of saying "anal penetration"). When that happens it is because receptors in the vagina are stimulated. She ascribes it to her g-spot (and that may be so) but likely she is getting off from the penis rubbing against the tendril of nerves that branch out from her clit and run back (among other places) along her rectum. It pays to do some slow exploration with angle of attack (not that you're attacking her ass), as well as rate and depth of penetration in order to maximize contact with the sensitive places next door.
There are some advanced pointers but they sometimes make folks go "eww" and this is long enough. I'll answer a few questions if anyone has any.
Anal Virgin in need of advice!
