A few tricks:
* use your hands & your mouth
* make sure you're really using your tongue A LOT
* press down a the bottom of his penis, on the side that faces him, in the crease where it meets his stomach. Use one finger longways, or two/three fingers. There's a vein here that takes blood out of the penis. If you press on it, not too hard, it'll keep in the blood, which increases his sensation and makes it puff up a little bigger. You'll feel it swell if you're doing it right.
* get used to it, some guys just take a long time. keep telling yourself how much you like giving head, even make yourself daydream or fantasize about it. it sounds silly, but you really can change how you think so you'll enjoy it more.
Stroke it and fondle the sac while you are giving him head
1. First you need to get him turned on - be more aggressive, grab his stuff, slowly massage his balls through his pants, it's important that you act as seductive as possible - the more you're turned on - the more he'll be turned on. Pull his pants down slowly and act as naughty as possible - this is a great turn on.
2. Grab his hand and lick on his fingers slowly before you give him head - just put his middle finger slowly into your mouth and suck on it, up and down, slide it slowly and moan - you have to moan a lot so he feels like a king.
3. As you're licking one finger, slowly start stroking his shaft (penis) with your other hand, you have to be on your knees and he should be standing, look him in the eyes - this way you can see his reactions. You need to love giving him head if you want him to really enjoy it.
4. Most girls make the mistake of being too soft - don't do that, grab his penis tightly and stroke it hard, as you're twisting his shaft with one hand slowly start sucking on the head (the tip) of his penis, curl your tongue around it, twist it in circles, then point it upwards and slowly lick it while you're watching him.
5. Say something like "mmmmm I love it" then smile, smiling is very important - it conveys that you love it. Keep on stroking and sucking harder.
6. Start talking dirty to him, put your hands around his balls and tickle them gently - make sure you are gentle 'cause his balls are very sensitive, as you're tickling, keep on stroking and sucking.
7. Once you see that he's getting closer start stroking harder - and don't even think about slowing down. Scream at him, tell him you want it - tell him where you want it (swallowing will make him go crazy just as you want it) - then as he starts to come, you have 2 options - you can hold his penis or he can hold it - I suggest you let him hold it and squeeze it out.
8. Then hold his penis and stroke it slowly, just as if you were trying to squeeze every last drop out of him into your mouth, give it a few more finishing licks.
9. Then smile at him, open your mouth and show him what you've got in your mouth, smile, then swallow all of it - then look up at him again and open your mouth to show him it's gone. If you REALLY want to learn how to give a blow job then you have to read Jack's Blowjob Lessons ----> link
10. Smile again, believe me he'll love you for it.
Put your ass in his face in a 69 and let him sniff butt hole as You suck.
Never neglect the balls!
mix it up and definitely try to be creative and to understand the physical sensation that you are creating...
but, the key is the mood and the experience. Guys can come very easily, but we (especially with age and experience) usually can control that and hold out for a long time. Its more mental than you might think. Blowjobs feel great and they stimulate orgasm pretty damn effectively but its more the feeling that someone else is doing that for you then the actual sensation that matters. Eye contact, talk, what you're doing with your hands are all important. The key for me is believing that you enjoy doing it and that you enjoy that it makes me feel good.
You could have him look at porn beforehand, or just masturbate to you, when you're naked.
All the suggestions from other answerers will help, but above all you shouldn't put too much pressure on him to finish as that will make it more difficult. Sexual performance is about giving and receiving pleasure, not about how quick,how much you come etc. Concentrate on enjoying it and seeing to it that he does too!
while your giving him head suck hard not too hard lol, get one of your fingers wet, push it inside of his butt all the way, and move it around a little, he won't last more than a couple mins. sorry don't know how to put it in a polite way lol