Names are important descriptive devices. If you're writing a short story or a novel, you may need to change characters' names several times, as you learn more about them, and the names you chose initially no longer fit.
Pay attention to names in the novels and stories you read. Some writers are excellent at inventing character names. Read Reginald Hill's Dalziel and Pascoe novels; Hill's a master at inventing character names.
Keep a notebook to collect character names. Obviously, if you plan to use the name of a real person in one of your novels — don’t. However, you can mix and match names, and change the spelling.