Explore New, Uncharted Territory
I know it's a delicate topic, but anal play is getting more and more popular and you need to know about it. Why? Because if you get it right, he'll have the most powerful orgasm he's ever had. (Yes, really.) Having said that, his bottom is a hugely private zone, and you'll need permission to enter. How? Either ask outright or read body language—ideally both. Instigate proceedings by stroking the perineum, the smooth area between the anus and testes. Then use three fingers to massage it firmly. Let your fingers casually brush against his anus and see how he reacts.
If he pulls away or clenches his bottom together, he's either not interested or nervous (quite possibly both). If he lifts his bottom or presses against your hand, it's a pretty good indication that he'd like you to continue. Keep stroking the opening until he's relaxed again, then insert the tip of a finger into his rectum (having first applied some lubricant you left on the nightstand). Hold still for a moment or two, then try circling or moving your finger gently in and out. Check that everything's fine (just say, "Okay?') before pushing your finger further inside. Once you've gently explored how deep and what sort of movement he likes, add it to oral sex or when you're masturbating him with your hands, just before he's about to orgasm.
Ban the Bed
Yes, you've heard it before: Sex in the bedroom is boring blah blah blah. So... why don't you stop having sex there then? Knowing you should be having sex in places other than the bedroom won't turn you into a better lover unless you do it. Have a quickie in the bathroom at parties or in the lavatory on an airplane. Let your hand stray into his lap in the movie theatre. Give him a very naughty, long, wet kiss in the kitchen at his parents' (though not while his Mum's doing the dishes). Pounce on him in your living room, dining room, spare room. Do anything beyond rolling over once at the end of the day, stifling a yawn and making a half-hearted attempt at fondling him.