I'm not sure if it is because I look a bit androgynous, or if it is because my site is designed to be a resource for sexuality, but I get a lot of people who are seeking advice on anal sex for the first time. I've decided to compile my best advise on how to start with the butt stuff...

DISCLAIMER: This is not an encylopedia of all things anal; this is just a simple guide to get you started.:

Where to Start?

The anus. The butt. The ass. The derriere. Everyone has one, and in the world of human sexuality, any orafice where a penis fits is considered an option for sexual intercourse.  Some people have a perception that anal sex is painful, (and like anything, it can be if it's done wrong.)  But, for those who have done it right, it can be a source of great pleasure. (Guys, until you've had an orgasm enhanced by prostate stimulation, you're missing out.)  

So, how do you get started?

Supplies

• • Lubricant
    Lube is essential. The butt is not a vagina, and while it does have it's own protective layer of mucus, that is not anywhere near sufficient for penetration. When it comes to the butt, lube is essential on anything going in.  Ideally, you are looking for a high quality, water-based or silicone based lubricant*, depending on what you are inserting. 
    (* You should not use silicone-based lubricants on silicone toys.)
    
    Don't improvise, and use things like olive oil, water, soap, shampoo, or spit. If you must improvise, use a water-based lotion, baby oil* or petroleum jelly* (Vaseline®*).
    (* Oil or petroleum-based lubricants can NOT be used with latex condoms, as it will dissolve the latex.) 
    
    When it comes to anal, you can never have enough lube, so when starting out, always use more than you think you need.
    
  • Condoms or Gloves
    Whether you are getting it on with another person or people, or by yourself, condoms (or gloves if using your fingers) are a good idea when it comes to butt stuff, for two key reasons:
    
    • Your anal cavity is, essentially, a mucus membrane. Infection is possible if your toys or fingers aren't clean. With partners, disease is always a concern.
    • Condoms /gloves help keep your toys/fingers clean. Even the cleanest butt can be hiding some secret poop somewhere, and removing a condom is way easier than scrubbing that expensive toy or getting feces off your hands!
  • Fingers
    Before inserting anything sizable, always start small- with one finger, then add a second. It is always a good idea to allow your anal muscles to stretch and adjust to something going in instead of just out before going with something larger. 
    
    I know there are a lot of pornos and fictional stories that skip this step, but trust me, butts are always traumatized by sudden entry. Go slow.
  • Toys
    My personal recommendation is, once you get past the finger stage, to start out with a small butt plug or anal beads. (I suggest glass or stainless steel plugs or beads, as they are easiest to clean and keep sanitary.)  Beads are great to start, since they will let you put items in without having to apply much pressure for your muscles to stay relaxed.
    
    Remember, the average rectum is around 12 centimeters, (around 5 inches) long, so plugs work better for beginners than dildos or long toys; you can work up to longer things once you've developed technique, control, and know your timing.
    
  • State of Mind
    Like most sexual activity, if you're tense or scared, you're not going to enjoy the experience. If you are tense or scared, do not force yourself (or anyone else)!
  • Paper Towels, Wet Wipes
    There is a risk that you'll make a bit of a mess. If you're playing on your bed, or upholstered furniture or carpet, I recommend using a pet pad underneath yourself for safety. Have some paper towels, toilet paper, or wet wipes ready.

What You Need To Know

• • Anal sex is never portrayed realistic ally in porn. Ever. 
    This is rule number one for a reason. Too many people, (males particularly) take many of their cues about sex from porn. Essentially, when it comes to anal sex take everything you’ve ever seen in a porn and throw it out the window.
    
    Actors in porn who are going to do an anal scene prep extensively beforehand so that they’re ready when the camera starts rolling. If you take a porn scene approach with someone who hasn’t prepped beforehand, you are going to wind up with a very, very angry partner, who is probably in pain, and who has probably made a mess.
  • You're not using enough lube.
    There is no such thing as too much, but there is definitely too little. Be liberal and generous with the lube!
  • Go at their pace.
    If you are the one doing the penetrating of someone else's butt, go at their pace! There will be a lot of stopping and starting. If they say “stop” or “can we hold still for a minute” then stop and hold still for two minutes. Caress, kiss, touch, and be patient.
  • Exploring strange new worlds.
    Treat anal sex like you’re an astronaut in the 1960's. First time, you may be going into space but you’re probably not staying up there very long. Think of it as a test run just to see if it is feasible. Like the first space missions, it will most likely take you several attempts before it works well, and you're ready for a full moon mission.  First couple times - be prepared to call it a night prematurely. Just accept it ahead of time and be pleasantly surprised if things move ahead of schedule.
  • Tension is a thing.
    You or your partner are likely to be tense the first few times with anal. Tension is a killer in sex. It takes a person out of it physically and mentally, and more to the point causes one to tense up an already tight area of the body. The mind may want to do it, but the body may have other ideas.
    
    The tension may come from a couple of sources:
    • It Hurts. How much will vary person to person, but it will hurt and pain causes tension.
    • Fear. You’ve seen porn. They've seen porn. They know you want to go at it hard. They are placing trust in you that you won’t until they are ready. Every time you get impatient, or push in when they've asked you to hold still makes them more tense.
    • It is awkward. A cock moving around in your ass can make you feel like you need to, or worse are going number two. Going number two on your partner is a mortifying concept for most of us. It takes some getting used to, and early on it is going to create tension until there is confidence that isn’t going to happen.
  • Breathe!
    Staying relaxed while something painful/pleasurable is happening to your body is hard, but open mouthed breathing helps. Keep an eye on your breath, and theirs, and remind the bottom/sub to breathe - it will be painful at first and often times we inhale sharply and hold our breaths when something is painful (think about getting a shot at the doctor for example). Deep breaths help.
  • The Sphincter is a muscle
    Important idea here. I often hear or read about people worried about getting “stretched out.,"
     or loose “back there” afterwards. That’s not really how the body works. The sphincter is a muscle, and like all muscles if you exercise it will become more limber and flexible. You wouldn’t go to yoga and worry that your arms/legs were going to become all “stretched out.” Think of anal sex as yoga for your ass.
  • Prep
    If you find you like anal sex and want to enjoy anal sex more, then prep for it. Buy a butt plug or three. If you think you’ll be having anal sex that night then insert one for a spell. Work up to one that is analogous to the size of your partner’s cock. If you’re worried about the mess then douche ahead of time. There are several easy to use kits available at your local pharmacy or through your favourite mega online retailer.
  • The Mess
    There will be some mess, and it’s never “their mess” - it is always “our mess.” Critical semantic difference. It may have come out of their  body, but the only reason it did is because you put your cock in there. To repeat: there will be some mess. Get over it or don’t stick your cock in someone’s ass.
  • Ass to... nothing.
    Nothing that has been inside an ass should make contact with a vagina or mouth immediately afterward. Nothing. This is another place where porn is bad information. In porn, actors go back and forth between rectum and pussy like they’re interchangeable.  Bad idea.
    
    Naturally, the rectum is full of bacteria that has the potential to cause an infection. Vaginal sex after anal sex is a terrible idea - it transfers those bacteria, which will cause all kinds of painful vaginal and urinary tract infections. 

The prostate: The male g-spot

The prostate is a walnut-sized gland, located just behind the bladder. It can be reached internally (via the anus) and externally (via the perineum (taint).

Generally speaking, if someone is laying on their back, insert your finger or toy, and slowly-- and I mean slowly, move your finger in an upward position towards the front of their body. Gently feel around. The prostate feels like a rounded bulb of tissue, similar to the tip of your nose. It is generally around 5 centimeters (2 inches) inside the rectum.

For many, moving your finger in a beckoning, "come here", motion against the prostate is pleasurable, but talk to your partner about what feels good, and what doesn't. Faster? Slower? More pressure? Less?

Massaging the prostate can sometimes cause the release of a milky fluid. This is why stimulating the prostate is sometimes referred to as milking. If you see milk, keep going, because orgasm is on the horizon.

Stretching

Ok, you've dipped your... toe into the world of anal sex, and find you like it, and now you want to work your way up to larger toys, or maybe even a fist.  Remember, your ass is a muscle, and before you can do some heavy lifting, or some deep stretching, you'll need to exercise and work your way up.  And, like any exercise, you need to keep it up to continue to do the heavy lifting.

Your sphincter's entire purpose is to accommodate a massive toy or wrist, it is to keep feces in your rectum and let it out only when you are ready. It will tighten and restrict. It will not get loose, no matter how big you go. Anal penetration gets easier because you develop better control, not because you've gotten a looser sphincter.

Fingers are always a good way to start, (and I reiterate that I recommend gloves for safety. Dilators (which are medical devices which you can find online) are also used for pleasure, and a reasonable way to practice stretching to accommodate larger things. 

Butt plugs often have narrow tips and taper into a wide point, then down again to a base. The flared base prevents them from going in all the way, preventing you from becoming one of the emergency room statistics that any ER nurse will gleefully share with their friends. Plugs come in all shapes, sizes, and materials, and are a good way to work your way up, starting with a smaller diameter plug and working up to larger ones, or consider an inflatable plug for versatility.  There are even trainer plug kits out there for this very purpose. 

If you want something more realistic-- or not-- a dildo is the way to do. They come in every shape and size-- from ultra realistic penises to alien and otherworldly things. 

Regardless of what you choose, be sure the material is body safe. Avoid toys with phthalate, and look for BPA-free. Silicone, stainless steel, and borosilicate glass are great because they are non-porous, and easy to keep clean,. For beginners, silicone* may be better, as it has a bit more flexibility and give.
* Note: Silicone-based lubricants will deteriorate silicone toys, destroying their non-porous nature and exposing your mucus membrane to harmful chemicals. For silicone toys, use a water-based lubricant.

If your goal is to continue to stretch and increase your capacity, you should aim to train once or twice per day, at least 5 days a week, for 5-10 minutes at a time. Stick with a size for a week or more before working up to the next size. If you feel no resistance or discomfort when inserting, you're ready to move up.

Will anal make me gay?

Only if you do it right. Honestly, if you find yourself having gay desires or fantasies, you may want to explore that, and it is highly improbable anal sex was the root cause.

Anal is not for everyone

When all is said and done, anal penetration is not for everyone. If you find you don't enjoy it, that's fine-- explore something else. If your partner doesn't enjoy it, find something else. But, for many, it can be extremely enjoyable.