This comes from one of my fave bloggers and writer-guys, Chuck Wendig. He can be a little raunchy with the tips, but he’s always right on.
What I really like about Chuck’s tips here is that he nails the importance of good dialogue and its role in plot. Here’s a taste:
3. Sweet Minimalism
Let’s get this out of the way: don’t hang a bunch of gaudy ornaments upon your dialogue. In fiction, use the dialogue tags “said” and “asked” 90% of the time. Edge cases you might use “hissed,” “called,” “stammered,” etc. These are strong spices; use minimally. Also, adverbs nuzzled up against dialogue tags are an affront to all things and make Baby Jesus pee out the side of his diaper, and when he does that, people die. In scripts, you don’t have this problem but you can still clog the pipes with crap if you overuse stage directions. Oh, heavy dialect and sland? Just more ornamentation that’ll break the back of your dialogue.
6. Shape Determines Speed
Short, sharp dialogue is a prison shiv: moves fast ’cause it’s gotta, because T-Bone only has three seconds in the lunch line with Johnny the Fish to stitch a shank all up in Johnny’s kidneys. Longer dialogue moves more slowly. Wanting to create tension? Fast, short dialogue. Want to create mystery? Longer, slightly more ponderous dialogue. Want to bog your audience in word treacle? Let one character take a lecturing info-dump all over their heads.
And there are 23 more, just waiting for you to peruse
Happy writing, happy reading!