Previously you had to sign up for USAA while on active duty, but as of today they are allowing former military personnel in retired status or honorably discharged to sign up, regardless of service dates. I do all of my banking (checking, savings, investments, insurance, mortgage, auto loans, credit cards, etc.) through USAA and I've always had great experiences with them, so I thought I'd pass this info along.
Also, once you become a member, your spouse and children are automatically lifetime members.
