Another difficult thing to do is make it all sound natural, dialects, accents etc. without making in cliched and twee. I have read so many books where they tried so hard to use dialogue to tell us who the character is that it spoiled the story.
One of the best books I ever read which massively exaggerated a Scots dialect was "Feersum Endjinn" by Iain M. Banks. Even me, as a Scot had some difficulty and had to actually say a lot of it out loud before it made sense.