[found on theguardian.com]
“It’s never too soon to start thinking about what your characters will say and how they’ll say it. Giving each of your characters a distinct voice is key to writing great fiction.
The goal of Worksheet 9 is to encourage you to think about your characters’ individual speech patterns and specific word choices. Your characters will probably reveal these distinctions as your story progresses, but thinking about it early will make you more receptive to such revelations.
For each of your major characters, record information about individual speech patterns and any catchphrases they may use.
With this information in place on a dialogue sheet, you’ll know exactly what a given character will say and how he/she will say it. You can also use this worksheet during the final edit and polish of the manuscript to double-check speech patterns.”