Building a relationship with the CEO of the most powerful music company in the world doesn't mean a thing if you don't keep in touch. You could befriend Steve Jobs himself, but it likely won't matter very much if you don't maintain that relationship. In fact, a great relationship with a less powerful contact can be far more useful than getting a business card from Clive Davis.
Here's some advice on how to maintain good relationships with your professional contacts:
Keep In Touch
Seems obvious right? I hope it does, because most people don't do it. Sure it may seem easy to keep in touch a few weeks or months after your internship, but will you actually continue to maintain that relationship for one, two, or even ten years. Keeping in contact shouldn't be about getting a job, it's about creating real relationship for the long term.
Try to Visit
If you'll be in the neighborhood, especially if your internship was in a different city, see if it would be ok to stop. Obviously, talking to someone in person is far more valuable than on the phone or internet.
Follow Their Work
This is easier than ever with Google and social networks. Did the label your interned at release a record that did really well or won an award? Why not congratulate them. Keep on top of what's going on with your friends and contacts and their companies. Conversations when you do keep in touch shouldn't just be about you, and this will certainly make it easier and keep you up to date with what's going on.
I'll have some more tips to up soon. For now, think about it, are you risking losing touch with contact you made at a job, internship, or anywhere else? What can you do to try to fix it?