Do what I did:
1. got my first credit card @ 18 from Capital One with $500 limit and 25% rape me APR.
2. never really used the card except intentional small purchases ($10-20) monthly and paid them off on time to build my credit.
3. about an year after, got an Discover Platinum with $1500 limit. Then shut down my Capital One and avoided it like a plague.
4. Shut down Discover when I got American Express Blue with 0% APR Intro/$3000 limit
5. That Amex has $8000 credit limit and my credit rating OWNZ (780+), I'm oh so young @ 21...
Tips:
1. never EVER be late on payment, they'll RAPE YOU SO HARDCORE ON YOUR CREDIT HISTORY!
2. keep your credit card limited to one. Two at the MOST!
3. always shut down accouts when you get a better CC. It helps cleaning up your credit history.