A net score of +3 may have been a little too much as there were only 3 eligible questions for the prize drawing. One of the concerns I had with the voting was the potential for abusing or gaming the system and also to draw out quality questions (which would also in turn spawn quality answers). There wasn't any evidence of that abuse or fraud at all during this contest.
I think our community is still very small that this didn't quite work out so well. For future contests, I would probably say at least a positive score of +1 might be a better requirement, but this number should probably scale or be modified depending on the size of the community and the audience we want to attract (new people, veteran users, and so on).
I haven't done much research into what other sites have done so pardon my ignorance on the format and rules of the contest.
Contest Topic and Community Participation
We ended up with a total of 10 questions related to tai chi, most of them asked by a single user. Participation was lackluster since only 3 users (out of a total of 468 (including the Community user) asked questions.
There may not be very many people who practice tai chi or have an interest in it in the community here as it is. Perhaps a different topic would generate more interest among the general community (and non-users of the site).
Unfortunately, the people I do know who are interested in tai chi wouldn't participate on this site (or on Stack Exchange or other internet communities in general). We could have advertised more, but I was wrong to think that the contest would generate more activity and new users when this contest was help in a small community with low participation.
What Contests Should Not Be
Money, prizes, and contests won't save or grow a site. These are extrinsic things that shouldn't dictate how or why the site should grow. This has to be something that comes from within, originating out of the community here for the community. Pulling in new users is a bonus, and I don't think we have a substantial enough amount of core and interested users to do something like this really well at this point.
I had originally tried to tie this in with World Tai Chi Day in the contest proposal. It's a nice idea to do these things in conjunction with one another, but I let it slip for a variety of reason. Nevertheless, I don't believe an event like that was crucial to holding the contest anyway.
For doing another contest like this, we need to continue growing our site and establishing a core audience. I'd like to see more interest in these type of things, but it is nice to see that people are visiting Meta and upvoting the idea.
Some other things to read: