I love editing, but there are always authors who make me want to get down on my knees and plead with them not to cripple their characters.
Dialogue is rarely grammatically correct. It mimics everyday speech, and often breaks ever rule that applies to written language. It shouldn’t be prim or proper unless the character is prim and propers.
Many authors write dialogue the way they think a character is supposed to talk, rather than how that type of character would actually speak in real life. I edited a book recently where I gently advised my client to adjust the vocabulary and speaking style of a teenage character to sound like an actual teenager. His weakness was that he spends little time around teenagers and being a more mature individual, didn’t have a good idea of how to write teenage dialogue.
Great dialogue mimics real life conversations and voices. A teenage character won’t typically sound like a retired professor. Yes, writing dialogue for multiple ages and genders can be daunting, however that is exactly why it is so important for writers to get out and listen to people.
Conversations take place around us all the time. Find a place to relax with a book or your laptop, and sip coffee as you listen to the people around you. Take note of how people of various ages, backgrounds, and professions speak. Note where they speed up, slow down, or pause. Get a feel for how everyday people actually speak to each other. Travel to different areas and listen.
In fact, start listening more in general.
Not only will you find inspiration for the dialogue in your manuscript, you may find that people find you more approachable and interesting as well.