How do u get "top contributor on Yahoo answers? and how do u earn star questions?

Being a top contributor has nothing to do with how many points you have, which is a common misconception on this site. There are top contributors who are at level two, and there are level seven users who aren't top contributors. Rather, being a top contributor has to do with how well you contribute to one to three different categories, excluding Jokes & Riddles and Polls & Surveys. If you keep receiving the best answer in the category or categories that you participate in, you will eventually receive the top contributor badge(s). Good luck!