Dos and don’ts for writing dialogue
Pay attention to each character’s different speaking style.
Edit dialogue to trim off most of the fat. A lot of what people say is just blah-blah-blah, but you don’t want to bore your reader.
Show how the character speaks instead of telling it. If the character speaks angrily, you can make this come through in her words — it’s therefore often not necessary to add an expressive dialogue tag such as, “she said angrily.” The same if a character is shouting or crying, etc. Keep the reader’s attention on your character’s speech, not your explanation of it.
Don’t get too colorful with the dialogue tags. “Hello,” she shouted; “Hi there,” he cried; “How are you?” she queried,” “Fine thanks,” he shrilled”… too much of this stuff gets distracting fast. Put your thesaurus away. The basic dialogue verbs “say,” “tell,” and “ask,” have the advantage of fading in the background, letting the reader focus on what your character is saying.
Don’t feel obligated to add a tag to every bit of dialogue. If it’s clear who’s saying what without them, then you can leave them off.
Don’t let your reader get disoriented. Use dialogue tags when they’re needed to prevent confusion. There’s nothing worse than stopping in the middle of an exciting scene to retrace the dialogue and try to figure out who’s saying what (“Okay, it’s the killer speaking here, so this must be the detective who’s answering him, not his sister…”)