I’ve been reading lots of self-pubbed authors recently, and one of the biggest comma errors I’ve seen, even in those works that have an “editor,” is a missing comma when someone addresses another in dialogue.
RIGHT: “John, where are the apples?”
WRONG: “John where are the apples?”
A humorous example that recently has been circling the grammar and writing sites is
RIGHT: “Let’s eat, Grandma.”
WRONG: “Let’s eat Grandma.”
These sentences not only are funny, but they are also a good way to remind yourself to put in that pesky comma when you are writing dialogue.