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.