Oh, some sort of ego the size of a jumbo jet, a complete disregard for common sense, an ability not to listen to the sound advice of others, etc., etc.! It's also nice if you can draw. Seriously, though, there are so many different types of art and so many different approaches that I can't really identify one set of skills that apply to everyone. And we all have different ideas of what 'success' means.

Develop business skills; constantly work at improving your art skills; try to avoid getting in a rut and repeating yourself; understand that relationships matter just as much as talent; work hard to develop your own vision rather than catering to trends.

Most important is to love creating art, because success may not mean financial security, it may not mean fame, it may not mean a full-time job in the arts. It may simply mean being happy producing work that you love.