Answers will be subjective, but here's a shot at some of the things I've seen:
- Very clear rules about what constitutes a good question.
- A community willing to enforce those rules and not just relying on a few uber mods.
- A community that is willing to be a little flexible about those rules.
- A sense of humor but one that doesn't get in the way of our serious business.
- A community that is incredibly civil by modern standards and generally more than willing to help out a newb.
- Getting some "names" to both support externally and answer questions on the site (people and corps).
- Solid UI. No bombardment with ugly ads. No hideous colors. It's not accidental that most successful websites don't go nuts with distraction.
And most importantly:
- Wide open arms for any language, framework, toolkit, IDE regardless of how esoteric.
- No fees unlike other exchanges of self appointed experts and no sign up of any kind required just to see an answer.