First you have to figure out: is this salary negotiable at all?
If you were coming to work for me, salary would not be negotiable. I pay people the right amount and don't negotiate, and so they almost always take it. Similarly, if you were applying for a government job, or a first job out of school at a big company, it's very unlikely that salary would be negotiable.
But if it is negotiable, you're going to have to negotiate.
There is only ONE THING you have to know about negotiation. Only one. When you know this thing, you will be a good negotiator.
Here is that thing: BATNA. It stands for Best Alternative To Negotiated Agreement. Google it. Study it. Live it.
The bottom line is: if you only have one job offer, and you need to work, you have NO alternative. Your negotiating position is extremely weak. You will get paid something near the bottom of the range.
But if you have TWO job offers, and you'd be willing to take either, then you are in a VASTLY better position. As soon as you have two offers, your suitors will have to pay you market.
When you have a compelling alternative, it won't matter if you're inexperienced or shy about negotiation. All that matters is that you have TWO offers in hand. You know why? Because you'll say, "THAT'S NICE, $65,000 IS NICE AND ALL, BUT JOE DOWN THE STREET WILL PAY ME $69,000 SO I'M GOING THERE."
The same applies to the company hiring you. Do they have anyone else who can possibly do the job you're going to do? No? Well, then, their negotiating position is terribly weak. They have to pay you whatever you demand, because nobody else can do it. There may be other alternatives. Maybe it'll cost them $500,000 if they leave the work un-done. OK, now they have to pay you $499,999. Why? BATNA. Their best alternative to paying you $499,999 is to leave the work undone.
This is probably not their position. They may have other people waiting to do the same job. Other people who will take $50,000. OK, now the best salary you can get from them is $49,999. Unless, of course, you have an offer from someone else at $70,000. In that case you're going to work for someone else.
BOTTOM LINE: Negotiating consists of one thing and one thing only: Lining up the best possible alternative that you can. In your situation, you need to get as many other job offers lined up as possible.
(They know this, so they may use various tricks to insure that you don't have time to line up additional offers. They might tell you that they need to hear back from you right away. This may be true, but nine times out of ten, they are trying to limit your ability to line up another job offer so they don't have to pay you market).
I've gone on too long here, so I'll stop. There are more details. Good luck.