You might think that having multiple graduate job offers won't be on the cards in the current economic climate, but if you stand out with one employer you may well impress others too and be in the lucky position of having more than one job offer.
If all the offers are in and on the table then you just have a decision to make. Don't base it on a quick win, eg taking the one with the highest salary. Weigh up properly what is on offer: How do all the benefits compare? Does one offer better training opportunities? Where did you feel the most comfortable with the culture? Potentially, you could progress faster and be happier in the organisation that has the lowest starting salary.
You've got an offer, but you've got more interviews to do
It is more likely that you will get an offer while you are still interviewing with other employers. Don't ignore the first offer: make sure you respond to the employer in some way, politely explaining your situation and asking what time they are happy to give you so that you can make the best decision. Again, most large graduate recruiters will be reasonable if you communicate with them.
Backtracking is a big No-No
If a recruiter needs a decision sooner, it's really your call as to what you do; you can accept or decline. But... and it is a very big but: once you have accepted an offer you cannot later change your mind. Your acceptance is a contract between you and the employer. Under graduate recruitment best practice guidelines, you must also remove yourself from the selection processes of other employers once you have accepted an offer. You can find out more about the guidelines for graduates and graduate employers through your careers service.
Don't burn bridges
When dealing with offers and negotiations the key advice is to keep in touch with employers and keep your communications professional. It's not savvy to try to play off different organisations, particularly the larger graduate employers. Recruiters tend to know each other and they talk. But they are also willing to talk to you and if they have offered you a job they will want to make your entry into their organisation as easy as possible.