Being a fresher, you are in a poor position to negotiate and so don't  
try.
Do your research and ask around to people who are doing similar kind  
of and get an estimate and based on this estimate decide a sum you  
think you are happy to live with for now. And state that price to the  
firm. If the company is willing to give you that, well and good. Or  
else give a straight no to the offer that is less than your estimated  
offer, but don't negotiate.
So this is it. Don't go into any negotiation.
It should seem like a foolish advice but I have seen this technique  
succeed countless number of times. How saying no and waiting bring  
back people on the table? How being firm on your resonanle estimate  
fetches you the job?
Stick to it and you will realize how much more worth you are.
Salary negotition is tricky business and HR people are trained in  
getting the most juice out of any job offer, so if you enter in  
negotiation for a job offer you are set to fail. So don't even try!!
