How to make your answer selected as best answer ;) ??

You just have to be knowledgeable in your answer, don't answer questions you don't know the answer for, don't be offencive or condecending in your answer even if you think the question is stupid. Genuinly try to help the person who asked the question

Put in as much detail and accuracy as you can, and make sure that you dont lapse off the point.

Thats if the question is a serious one though

well just answer the question and then put lots of details between the words well plz pick me as the best answer!

Give the best answer.

Try to be precise, and to the point.