Keep your promise if you accept an internship, even if a better offer comes along, to preserve a good reputation. The world is small.

By JOE GRIMM
If you have enough talent, connections or luck to get more than one offer at the same time, you’ll have to choose. During internship-offer season, the best and luckiest can get offers within hours of each other. Some offers arrive just hours after candidates commit to someone else.
For most, one offer is fortune [...]

With internships, there is very little room for negotiation. Because an internship is one of your first opportunities to handle a job offer, though, it is a first chance to start learning how to negotiate.

The most difficult career decision you might face can come when you must choose between competing offers. Unfortunately, this is most likely to happen early in a career, when you’re less experienced and have thrown out a lot of lines, trying to catch that internship or first job.

To negotiate the best job offer, do as I say, not as I do. When the Free Press asked me whether I wanted a job, I immediately said, “Yes!” (I think I yelled.) Not very cool, I know.