Get to know your characters. Figure out how they think and speak.
Give them their own original voices because if you can switch the names of any characters and still have the words they’re saying be in character for them, you know you have a problem.
Research. Know what time period and type of character you’re writing for. A rich CEO won’t speak the same as an inner city school kid. A modern character won’t talk the same as someone from fifty years ago.
Say your dialogue out loud. Make sure it’s something that makes sense and is realistic.
Dialogue should add to the story. It can deepen or move the plot along, add to relationships, or build conflict or tension. Just make sure it’s keeping the story moving and the scene interesting.
Going along with the previous point, remove pointless dialogue. A: “Hey, what’s up?” B: “Not much.” A: “Me either.” B: “Any plans this weekend?” A: “I think I’m gonna sleep in.” B: “Cool.” A: “You?” B: “No.” A: “How’s your husband?” B: “He’s fine.” A: “That’s good.” B: “Yeah.” It’s as boring to read as it is to write, probably even more so. Readers may skip it completely and maybe even end up missing something important in between all the meaningless lines.
You don’t always have to write it out. Instead of writing a pointless line, add to the story: “Are you coming over this weekend?” Lisa froze, then immediately began to rattle off a million things she had to do instead. Maria frowned. Who was going to help her finish the project now? She only had hours left and the presentation was still just barely started. Not the most exciting example, but you get the point. It’s much better than having to read… “Are you coming over this weekend?” Lisa froze. “Oh my gosh, I can’t possibly. I have to babysit then I’m helping my neighbor garden at one and my mother is going to be just furious if I don’t finish all my chores but I promised my dad to help him mow the lawn too and my brother wants me to help him beat this level he’s been stuck on his new video game. Oh man! I just remembered that I’m looking after my cousin’s cat all day tomorrow too. You’re allergic to cats, right?” Maria frowned. “You knew we had to finish the project! There’s only a few hours left to work on it! How am I supposed to finish it all by myself? It’d be impossible! We barely started the presentation! I don’t think I can do this…” The quicker you get to the point, the better for the most part.
Don’t use the same words. Words to use instead of ‘said’. This doesn’t mean you have to use 'avowed’ or 'beseeched’, but it’s beneficial to change it up sometimes instead of using the same few words.
Don’t be cheesy. Think about how you’d react if someone said these words to you.
Avoid cliches, or do your best to. These phrases lose their power over time because we get so used to them.
and in another round of GUESS WHO WE’RE DESCRIBING
“leather jacket on a golden retriever” “body of a late twenties urban lumberjack, eyes of a fifteen year old with an unrequited crush” “sexy teenaged firefighter” “gym addict build a bear” “soulful tracksuit poet” “back garden barbecue flip-flop” “lightly toasted crossfit marshmallow” “hard-working tube sock” “earnest chestnut horse” “emotional powerbar”
“I once had to look in the mirror and compliment myself for a health class grade and I couldn’t do it, says a lot about my self esteem apparently.I looked around wanting to cry because I knew that I wouldn’t be able to do that with people around me who thought otherwise.”