GREAT thread. FANTASTIC question.
Like any behavioral change, you have to couch it in positive terms. You can’t say anything negative, even if you feel like that. You have to encourage the positive.
I’ve had great luck with a simple mantra: “You’ve been with other/some/many men before, but you’ve never been with me. Let’s take the time to learn what we both like, shall we?”
Every woman I’ve been with has been different. Duh. Some things they like, some things they don’t. Some things they think they don’t like but come to enjoy because I enjoy them, and vice versa.
It all comes down to trust. I’m not judging your technique-- I’m coaching you to be the best for me. I like lots of spit, deep throating is fun to watch but feels no different for me, I need/really enjoy lots of hand action, eye contact makes it all better, taking your time is relaxing and makes the buildup that much better, being verbal makes it better, and keeping the change at the end demonstrates how much you enjoyed making me happy.
My last GF was super hot, fantastic in bed, and sadly gave the laziest blowjobs. She thought they were good, but they were just meh. Yes, the sensation was pleasurable, she was even enthusiastic, but her technique was tailored to the last man she was with, her ex-husband. It wasn’t about me, it was about her, and what she thought was best.
Alas, we didn’t date long enough to sort this all out.
My GF now was much the same-- she came into it with a rather lackluster technique. But she took the time to learn what I liked (and, again, vice versa). Now, as far as I’m concerned, they’re the best blowjobs on Earth.
Ladies (and men), it’s not a natural talent, and it’s not one-size-fits-all. Again, as noted in this thread, the one common denominator is enthusiasm, but beyond that, it’s about paying attention to what your partner enjoys.
Oh, and one other thing: porn isn’t life, and life isn’t porn, but trust me, you can learn A LOT about how to give a great blowjob from porn. Not every actress is good, but the good ones are fantastic. Take notes, ladies.
Finally-- Omniscient? That may be the single best, most accurate post I’ve ever read on SDMB. No woman has ever gone wrong with swallowing. Although, of course, under the right circumstances spitting can be just as hot. . .