There are all sorts of arguments in favor of credit cards and against credit cards. No one can tell you exactly what the right choice is for your particular situation. However, if you decide to be a credit card user, make sure that you are a smart credit card user. Don't pay unnecessary fees or high interest rates. How can you become a credit card guru?
Fortunately, Ramit Sethi of I Will Teach You To Be Rich is offering free online access to the first chapter of his new book, (also titled I Will Teach You To Be Rich.) The first chapter is called Optimize Your Credit Cards. I love that Sethi stresses personal responsibility but gives you the information that you need to be responsible. Note: This offer is still good, as of 28 June 2017. And it's still invaluable information.
The book, which will be released next Monday (March 23, 2009) is a 6 week personal finance program for 20-35 year olds. It focuses on banking, saving, budgeting and investing; what Sethi calls "the four pillars of personal finance. Obviously, he doesn't address the unique situations of military members, but he provides an excellent education in general personal finance - something that will be useful now and still after you leave the service.
Update: I Will Teach You To Be Rich has been one of the best-selling personal finance books for several years now. I've made my teens read it, and I'll encourage them to read it again when they get a little older. If you're looking for a great book to start learning about money, I strongly encourage you to look at I Will Teach You To Be Rich. It's good stuff