A good character?

Somebody asked me, “How do you know if a character is going to be a good one?” In roughing out a novel, I find I sometimes do not recognize the importance of a character until I am getting words on page. For you who have read the Bringer of Justice, Gula is an example of that type of character. For the second novel in the series, I have not gotten far enough for any character who I originally considered unimportant to come forward.