It's the same for every category, you Answer lots of questions and maintain your best answer percentage above 10%. Only give good quality answers, it will give you a better chance of your answer getting chosen as best. Answering about 10-20 questions a day would be a good place to start, thats how i did it. You could also vote for your answer when it is in voting. You cant get top contributor in polls & surveys and jokes & riddles.