The first time you receive notification that your loan is delinquent, be sure to contact your loan servicer or lender. Whether you just forgot to pay, or there was an error, choosing to be proactive is the best way to stay out of default. Your servicer or lender will usually work with you to keep your loan out of default as it costs them money if your loan does go into default.
For federal student loans, there are several Income-Driven Repayment Plans that may make your monthly payments affordable. There are also deferment and forbearance options available in certain circumstances. Your loan servicer can help you decide which you qualify for and what will be best for your situation. Remember: If your loan goes into default, you can no longer take advantage of these options.