Don’t abuse dialogue tags.
By this, I mean don’t overuse them. It’s not necessary to have a dialogue tag with every piece of dialogue. How many dialogue tags you need depends largely on how many characters are talking in any given scene. The more characters speaking in that scene, the more dialogue tags you’ll need to avoid confusion. If you have two characters, for example, you can leave up to three sets of dialogue without tags, and, if the conversation is between a male and female, you can often get away with leaving up to five or more sections of dialogue without tags, particularly if you insert action narrative in between. In the below example, some dialogue has speech tags, others action narrative, and still others have none, since it’s obvious from the context who is speaking in those places (if you had read this scene from the start).
“They’ve found it,” Vareck said.
“What? Where are you?”
“Standing over the body next to the weapon.”
Jacques was silent for a moment. “Just one?”
Unease creeping up his spine, Vareck glanced around the shadowy cavern, his eyes lingering on the dark corners where the wall torches’ light failed to reach. “Perhaps.” He hesitated. “Probably not.”
“You know what this means,” Jacques said.
“Yes. Gather the others and fill them in on the way here.”
“Give us half an hour.”
“I’m not sure we have that long.” Vareck hung up and scanned the cavern again.
Rule of thumb: if it’s obvious to the reader who’s speaking, leave the dialogue tag out. If it could be confusing, include it.
Extract from The Better Writing Guide.