a lot of bottoms who are a little tight seem to find being on top (straddling your lap) is there best position for'em, it lets them control how fast they take you and once they've losened up it's easy from that position to role them onto there back and you get to do the humping (both positions I like)
Doggy style is fun, lots of bottoms like that position too, some bottoms find this position most comfortable, just the way they are built and they have a bit of a say in how hard you can thrust in without having to say anything really.
Bottom on his back, on the edge of the bed, you standing, some guys it's comfortable for them if you pop a pillow under there lower back/backside, (pillow is good too if your a little taller or beds a little low) if you have a grippy floor and you grab there legs down near the hip you can keep them in place and really go to town on'em..
A fun one I've found almost every bottom I've been with has loved if you pulling there hips off the bed (upper body still on the mattress) and you carry there weight you can adjust the position of entry really well like this, you can raise them a little higher or lower too (depending on how your member points ;) ) but not recommended if you can't hold there weight long enough or they don't feel at all safe in your hands.
Bottom on his knees infront of you, you straddle his lower legs behind him, the bottom just needs to arch his back a little extra, push his backside towards you a little, you slide into him, great position because the top can thrust in, hold the bottoms hips, nibble his neck, let him rest his head back on your shoulder, kiss, feel his body, so on plus, the bottom can ride you too AND, you can push him into doggy or down on his stomach and you gown down with him (another member described this position which personally feels one of the best when I'm bottoming)
Bottom on his side, you over his leg, his other leg over one of your shoulders (depending on how on the side he is) this position is a good one for guys who curve to the left or right (depending on the bottom of course)
If the guy is light enough for you to pick up, I haven't met a bottom who doesn't love being picked up and fucked, he can be looking at you or away from you, to get him up you can start by getting his legs around your waist, then slide your hands down your weight between his legs and your hips, turn your palms out, grab his upper thigh and most bottoms will instinctively (or what ever) will relex his hold on you your waist and you can start moving your hands into position while pushing his legs up, if he's flexible enough, it'll be really easy, the bottom just hangs his legs over your arms and your hands slide to his back, for most bottoms it puts his arse in the perfect position to enter and you both get the fun of something kinda exciting and having to be so close to each other, the bottom gets a kinda thrill to cause he has to trust you, your in control, your the dominate one..
picking him up when he's looking away from you... depends on which position you start at the one I mentioned before bottom on his knees, you behind on yours but the bottoms legs on the outside, you can lean him back and start taking his weight, but you need to stand up while carrying him and he needs to be kinda short, if he's a lanky bugga or heavy, just use brute strength and keep him close to the wall.
that's like a tiny handful of positions and there are hundreds more for you to find and experiment with, but, it's not so much the position that's important, of course if it's a comfortable position for you and the bottom, it's the whole package, how into you he is, how much effort you put into satisfying and hitting the bottoms spots, being passionate, communicative and most importantly, listening to the bottom, he'll tell you everything without saying anything, the way he breaths, the way he'll move slightly, his moans, his eyes, lips, what his hands are doing, his feel, legs, all these things will tell you...
But most important above all else, above everything, is to relax, enjoy your self and okay with laughing and enjoying your self, you don't always have to have penetrative sex, kissing, groping, exploring each others body by other means.. sex is suppose to be more then just getting off, it's experiencing each other.