Dialogue tips that actually work:
You are not writing a movie (ignore this if you are). The reader doesn't need to know every word the characters say for the duration of the story. Less is more.
Dialogue can happen within the prose. "And they awkwardky discussed the weather for five minutes" is way better than actually writing five pages of dialogue about the weather.
Balance your dialogues. Surprise yourself with a monosyllabic answe to a dialogue that's ten sentences long. Don't be afraid of letting your character use half a page for a reply or nothing at all!
Don't write accents phonetically, use slang and colloquialisms if needed.
Comma before "said" and no caps after "!?" unless it's an action tag. Study dialogue punctuation.
Learn the difference between action tags and dialogue tags. Then, use them interchangeably (or none at all).
Don't be afraid to use said. Use said if characters are just saying things, use another word if not. Simple. There's no need to use fancy synonyms unless absolutely necessary.
Not everyone talks the same way so it makes sense for your characters to use certain words more often than others. Think of someone who says "like" to start every sentence or someone who talks really slow. Be creative.
Use prose to slow down the pace during a conversation.
Skip prose to speed up the pace during a conversation.
