Without extra skills, a freshman can never be in a position to negotiate the salary. A college degree and a few internships can't help you convince the employer to offer you more than what he wants. If you have any special skill or expertise you can take the risk of negotiating with a prospective employer. Any potential employer has to invest more money to bring you to his expectations. So negotiating at an entry-level shouldn't be your priority in any case.
Think wisely
You can try if you think you are different from others and unique in some way. You must, in such a case, convince the prospective employer that you have something to offer. There must be a reason why you should be paid more. Let your head guide you when you try to negotiate. If the employer says that they don't negotiate, you coolly accept what they offer and get satisfied.
Take the chance
If the employer is open to negotiation, don't lose the opportunity to put forth your case. For this a bit of hard research is needed if you want to present a compelling case for yourself. Remember the key to any negotiation is homework, homework and homework. That means you have to seek the help of your school's career center, professional associations in your field and internet salary sites to get an idea of what salaries are given to people of your caliber.
Know exactly where you stand in the job market. Don't be overbearing; have respectable attitude while broaching the salary issue. At no point, you should give any hint that you are entitled to a higher compensation. You can politely tell the interviewer that you have a specific skill and ask them whether that is something worthwhile to them and if so, would they be open for negotiating a higher package. You may not get what you want, but you won't lose anything.