I've had some in mind, but it is only when I really need to have a character, that I get serious about creating one.
Today I did some sketches, and the first character that emerged has dark hair, and is a 'girl-next-door' type. After I drew her, I thought that she might look like a character from the strip, LuAnn. So I checked, and have decided that my character looks unique enough, i.e. unique enough to be a new character in the LuAnn strip. But since, I'm putting her in my strip first, I've got dibs, so there.
I've not finalized the character, but I'm going to add her, anyway, and develop within the strip. And as an extra added bonus, you get to watch my (her) progress as it happens!