Do you want your readers/viewers to like your protagonist?
According to a report on the Psyblog.com site, the five most attractive personality traits are:
- kindness and understanding
- a sense of humor
- being fun-loving
- having an exciting personality
If you want to make your protagonist appealing, let them display a couple of these within the first few pages of your novel or screenplay.
I'd say the trickiest is "exciting personality," which is open to interpretation. For sure, don't have your character declare that he or she thinks they're zany, that's usually a sign that the person is particularly boring.
If you have a character whom you want readers/viewers not to like, let him or her display the opposite of one or more of these five.
Of course, while you're at it, you could also check whether you've been displaying these five in your personal life...