Tease him with your mouth while his hands are out of the way. Make him ache with desire. Talk dirty to him.
role play. pretend you're the cop and he's the prisoner, would that help you be more aggressive?
Tease him, and keep him on the edge of orgasm for as long as possible... all tied up, there's nothing he can do about it ;)
Go down and start sucking his balls, and then his penis.
The most interesting thing about bondage (in my opinion anyway) is that it lets one person let go of all defenses (at least psychologically) and the other gain control. It's a really cool thing in a way because it's a sign of complete trust...on both parts! Your boyfriend is trusting what basically amounts to his soft underbelly to you, and you're trusting him to allow you to take things a bit further than he might normally think of as his comfort zone (pushing the boundary is fine, but don't break it! Make sure you've got a safe word. ^_^)
In any case, do things he might usually shy away from. You can start with touching parts that people usually protect, like the sides of the torso (usually defended by arms!), the neck/jugular, insides of the thighs. Once you've gotten a bit more comfortable, you might try something more naughty, like spanking! >8D Do things that make you a little nervous, but not things that make you upset. =)
Be sure you know how to use the handcuffs safely and efficiently. Use only police quality handcuffs, not the cheap ones with a lever for double locking. Cuff his hands behind his back, palms out, key holes up for maximum security. Make sure the tightness is right; you should be able to put the tip of your finger between his wrist and the cuff. Then, double lock the cuffs (probably requires putting the tit on the top of the key into a slot on the handcuff) to prevent further tightening. Check from time to time that blood circulation in his hands is good. This shows the man that you care about his safety and know how to use the gear. Then, explore his body with however much abandon and joy you can find. Use your fingers, hands, lips, tongue, teeth, and nose on his body, all over. Watch to see his genital reaction; some things will work for him; some will not. Nibble on his t*ts and genitals. Taste (or at least, smell) his armpits, genitals, and whatever sweat or precum he produces. If you are both aroused, see if vaginal penetration is possible; it would be painful for the man, cuffed like that, to lie on his back, so use your ingenuity on positioning. Oral sex from him or to him is certainly possible while he is cuffed. He might enjoy continuing verbal encouragement from you, praising his body and especially his genitals and muscle, man-smell, studly appearance, whatever you can honestly say in his favor. He might enjoy verbal abuse, though I don't encourage that, not if you want to preserve his self-esteem. Still, some men become aroused through verbal abuse. On a later scene, add police-quality leg irons to his bondage. For variety, cuff him while he wears button-fly jeans, and maybe let his genitals out of the jeans during the event. With a little care, the experience will be fun for you both. You'll know the event was a success if both of you want to repeat it. (Police quality gear is available online, but I hesitate to mention a particular source because that might appear to be advertising or spam.) Consider whether you would let him do you the favor of reversing roles.
As others have suggested, just do what you want to do - you are in control...
You could always just leave him cuffed while you do something else - it might turn him on, for example, to know that you are phoning a friend and talking to her about 'normal' things, while perhaps ignoring him or playing with him. You might want to worry him by talking to your friend about the fact that he is cuffed and naked beside you (depends on your friendship with your friend of course).
You might also want to consider leaving him alone for a period of time and see how long he can cope being unable to move ... and, if your situation allows, being more daring by inviting friends around whilst he is unable to escape - not to show him off or anything like that, but having the frisson of excitement that one of your friends could wander in on him. Make sure he is happy with others possibly getting involved first, of course (and that you would be as well).
Get some ankle cuffs as well to make sure he can't run away.
If he's wearing old cothes, you could always cuff him and then cut or rip his clothes off of him.
The possibilities are limitless ;) Have fun!
if he is submissive, you may want to see if he like anal play (his rear not yours).
Its a touchy subject, but you can run a finger by his anus, then judge his response.
This made me lol! Well it's all up to you. It's best if both of you have fun!
take control don't think about him really make him please you do whatever YOU want to do
tell him to be quiet could play hit or spank him (saw the bad boy thing below)
tease him sexually start and stop make him REALLY want it
sounds like a lucky dude
its cool tht you are giving this a chance and trying this out (jus wanted to share my opinion)
think of it this way, your in control while he's hand cuffed you can do anything to that body you want, sit on his face, suck his cock, shuv your t*ts in his face, ride him any way you want :-)