Hi Mr.Vignesh
Welcome to CSR, This is a common question everyone asks after joining, i will tell u from my experience whatevr i know and rest will be asked by other experts, first go about reading all the Guidelines given for posting and know all the rules of the site well so that you dont commit mistakes and regret later.
Go through all the sections of the site one by one in detail and analyse what is going on which will give you a fair idea.
Then finally choose two three top earners profile and see what all they have contributed to earn there points and i guess you will become half expert and remaining is for your action.
All The Best!