Now that you've decided to look at dialogue to revise, how do you go about this. When I first began writing, I used to take segments where the dialogue was heavy and isolate it from the rest of the mss. The segment looked like the script of a play without stage directions.
First I went through and tightened everything. Getting rid of repetitions except where the repetition was needed. We've all seen segments of dialogue where one character repeats, maybe in different words, but it's the same thing that character A has already said.
Then I sharpened the dialogue, making sure each person said what I meant them to say. This meant sometimes adding and sometimes subtracting words.
The third step was to fill in the blanks. Sometimes a character was leaving out too much and making the reader guess. Those were often signified by the -- or the ... moments in the dialogue.
The next was to make sure the character's dialogue was true to their nature. People in different professions and different social milleaus use different words. Making sure their dialogue fit their nature helps individualize your characters.
Finally I read the lines aloud for rhythm and sense. I now read it in my head. Reading dialogue aloud can make people look at you in a strange fashion.