It not hard or mysterious, but the first time can be a bit daunting. I remember going through the forums and 'how to' when I was trying to cross this bridge, and now, ten years later, I thought I'd offer some hard won advice to other men.
Now, you could be in one of two positions; one, you have a partner who's willing to give it a go and are looking for the nuts and bolts of how to do it right. If that's you, you lucky devil, skip straight to the second section on getting it in there. Or two, you haven't quite got the 'ok'. If that's you, read on about popping the question.
The proposition
You can't just jam it in there; surprised don't end well, trust me. But equally, you're chances of getting a yes from a sit down, serious conversation aren't great. Your best chances are when she is highly aroused after some serious foreplay. This is for two reasons, one being that anyone who's aroused enough will do things they would otherwise never consider, the other being you're in a position to go through with it before she has a chance to change her mind. I stress the arousal - if you have to pull out half way through conventional sex, then do it. You want her to be very, very, hot under the bonnet.
Getting it in there
Let me start with some fails:
โขSurprise anal - I say again, serious fail. You'll probably not only hurt her physically but you'll piss her off as well. And then you'll never get another chance.