Student(s) with no income
You should always file a tax return, even if you do not have any source of income. Filing tax returns of $0 is actually a good thing, because it's additional documentation that you have no income, and therefore demonstrate need. If you need to contest the results of your FAFSA later, having tax returns showing little or no income will help you.
Starting February 3, 2014, students can use the IRS Data Retrieval Tool to auto-fill the tax section of the FAFSA.