I'd say it's usually best not to stop once you've started.
Use your hands, all over a woman's body and on a man's "pleasure points" (shaft, balls, nipples, butt).
Find your partner's preferred rhythm and maintain it, while switching up other things, like the amount of pressure, length of stroke (etc). I have been with a couple of women who enjoyed when I switched up the rhythm, but every other woman I've been with (and the one guy) all preferred a fairly slow and steady rhythm.
If your partner's attention wanders, a little pain can be a great way to bring their focus back to here and now. I'm talking about nipple squeezing, a (fairly) gentle bite or a playful slap on the inner thigh.
Ask your partner yes or no questions while pleasuring them. Such as: "Faster?" or "Firmer?"
Ask your partner for feedback/suggestions after they cool down after cumming.
A dildo about the same size as your partner's penis can be great for practice and improving your skills. When practicing, concentrate on maintaining your partner's favorite rhythm. Most guys love deep throat, and will really appreciate it if you learn it.
Most important: have fun
and let your partner know you love what you're doing. A simple "mmmmm!" goes a long way--and it's easy to do, even with your mouth full!