One big mistake both sexes make with the pace of oral sex is they do it like they would like it done to them. That's great if you're gay, but if not it doesn't work so well.
Women like to be taken right up to the edge of release and then dwell there with carefully adjusted pressure and timing. Doing that to a man will make him nuts. There is a point somewhere around 80% of the way there where he just wants to shoot. To reduce stimulation there doesn't result in a better orgasm, it results in less. Up to that point, the slower you do it the stronger it will be. Sorry, we're tricky.
The way to tell if he won't vocalize is that is the point where he's going to start pushing or wiggling. From there, get the job done so to speak.
Now before that point where he just wants to get off you have a big control over how big the orgasm is. Use this to your advantage. If you want some in return RIGHT AWAY, don't dwell there. Take him through quick and while the orgasm isn't as strong, he's going to want to be quick and aggressive with you. On the other hand, if you linger there for long enough, he's going to be spent. He's just going to want to snuggle and hug for a long while.
You got good advice already on where to stimulate a man early. Tongue play around the frenulum (the triangle on the bottom of the head) and around the rim is heaven.
Once you get further along, it is the feeling of thrusting that takes a man further along. If you want a quicker pace, use a hand under your mouth. BTW, don't slide around on a man without lubrication. Your spit works good or use a lube; or just move the skin up and down without sliding over the skin. Since men don't self lubricate, it doesn't take much to cause a bit of chafing.
If you really want to pick up the pace, concentrate your lips around the bottom of the head. When you move your hand up and down it will pop the rim in and out. You can move your hand WAY faster than you can bob your head. I bet you'll be surprise just how fast you can get the job done doing this. Again, use it to your advantage based on what you want to do next.
And at last some on finishing:
This goes to the basic urge for sex that men have. They do have a strong desire to plant their seed. Since pulling out during orgasm doesn't do that, there is a strong desire to feel like it is in deep during orgasm. When he starts orgasming, don't stroke and most of all don't slide around on the head. You've probably already found out about that during intercourse if you're really close when he goes. Sorry, it is just rather unpleasant to stimulate the head during orgasm and he's going to pull back, which goes against the strongest desire during orgasm.
The most important point is that if you're going to move your mouth off, don't suck or pull on the way off. Open and then move away without making it feel like pulling out. If you're gong to leave it in there, put the end against the roof of your mouth and put a little pressure on. (oh, and he's a lucky SOB if you do
If you do pull out, put your hand around the shaft and then put your thumb on the head. Push down a bit while he's shooting. MAKE SURE you don't PLUG THE END WITH YOUR THUMB THOUGH. That's bad, it over-pressures the plumbing in a very bad way. Finally use your other hand to push down a bit on his pubic area.