What should a webmaster need to do when his hosting account is suspended??

You will probably need to contact the support guys from where you got the account. Can you specify the exact reason for getting the account suspended. I mean there can be various reasons for excessive SQL usage to illegal usage. Anything can be possible and you can have you account gone for a number of reasons. Please keep a comment with why you got the account suspended. If you have no idea then it is best to contact support.