It's a good question, and one that I struggle with too. The best advice I got on dialogue was that you can use the description/action to show pauses, which allows you to control the pace.
E.g.:
"Boo," I said.
"What?" he asked.
"It's Halloween," I said.
Versus:
"Boo," I said. The window fan buzzed, just barely audible over the traffic in the street below. I smelled sweat and sewage blowing in. The glow from the TV in the other room flickered blue, then red.
"What?" he asked.
"It's Halloween," I said.
Adding the pause in Version B can let you add overtones of menace, romantic tension, boredom, etc. etc. depending on the context. Conversely, you can speed up your dialogue by taking out the descriptions- up to you to decide when and where it's appropriate.