ONLY use this .gov site to complete your FAFSA!
Use this PDF as a practice sheet so that you know exactly what will be asked when you complete the online form.
Not as comprehensive as the Practice FAFSA above, but offers an overview of FAFSA sections and information needed.
If you have a question, someone else probably does too. Consult this list from StudentAid.gov (the official site!) for help.
Excellent guidance in multiple short videos from StudentAid.gov. Overview of the Financial Aid Process is very good, as are others.
The CSS Profile is completed through the College Board.
A few hundred schools use the Profile. Consult the list.
Khan Academy-produced videos for each section.