My greatest help in giving realy good oral has been
Sweeten'd Blow- it tastes good without being icky, provides great lube for me to get my hands involved, and the lube lasts a long time. I take a little in my mouth, swish it around to dilute it, then go to town!
I think a lot of the turn on for oral is the guy knowing he's getting something special. Guys want your attention, and giving head is a great way to let your guy know that he's getting your undivided attention. I like to lead Martel in the bedroom, have some candles going, that kinda thing. Blindfoling your guy for part of the proceedings (like in the beginning) can be really hot, because it gives him a bit of a sensory overload.
Kiss him, lick all over his body, rub his feet- get his juices going before you ever get to the "main course." If he likes nipple play- play with his nipples! Excite his whole body (part of the teasing that was mentioned earlier). Use fun props like a feather, or a soft silk scarf, or your hands to rub his body and playfully rub his genitals- it'll excite his sense of touch and make him more sensitive to the blow job.
As to technique- I use my hands and my tounge a lot which makes it easier to go a long time. I also like to get really messy- using a lot of spit, getting everything really lubed and such (this is a lot easier if your guy will trim his pubic hair- or better yet just shave it off). Long slow licks with the tounge are appreciated, as well as kisses and licks all over the general area. If your guy likes his balls played with, play with them! Take them in your mouth, suck on them like a Cadbury's egg, that sort of thing
Giving head is the best when you're into it, too. When you're doing it because you love your man and want him to feel good, it becomes something that you two are doing together instead of something you're doing to him- and that really makes it stellar and special. Love him and show him you love him while you're giving him head, and it'll be out of this world!