First you should understand your loan agreement, make sure you know all loan info, and make sure to get ahold of your loan servicer when you might have trouble making your payment.
Have you missed a payment or made a payment late?
Yes, I have missed a payment.
Then you would be considered delinquent and late fees probably will be added to what is due; but there is a chance that you could avoid default by contacting your loan servicer.
Is there an easy way to track my loans online?
Yes, you can find out about all your federal student loans from the US Department of Education by signing in to "My Federal Student Aid".
What are the most important steps to avoid default of student loans?
Always try to avoid default first of all and take the time to comprehend your loan agreements and what are the exact loan types you are getting; and never borrow more money than you need or more than you expect to pay back.
What should I do if my federal student loan is delinquent?
You should look into the Student Loan Debt Collection Assistant, which the US Department of Education developed along with Consumer Financial Protection Bureau because it has tools that will give you access to special repayment options.
What is my promissory note?