When you have a set of characters, you have to fall in love with them and care about them as each individual character.
I felt like that character in Flowers for Algernon. Not Charlie, the lady teacher from the college who realizes, 'I've got to stop dry-humping this mentally challenged guy!
Finally the world would see my full range of comedy characters - from grouchy librarian to Russian librarian.
Your characters should be as smart as you are, if not smarter.
If you care about [the characters] as if they were real, that always helps.