What each form is asking for, why it asks, and what to have ready before you start.
Most of the difficulty in a financial aid form is vocabulary rather than arithmetic. Terms like enrolment status, dependency, household size and untaxed income all have specific definitions that are not quite the everyday ones, and getting one wrong is the usual reason a form has to be corrected later.
Read the whole form once before entering anything. The official instructions define every term, and the definitions are the part worth reading closely.
Commonly needed: identity documents, prior-year tax information for whoever the form asks about, records of untaxed income and benefits, and the list of schools to send the information to. Exactly whose details are required depends on your situation.
Gathering these before you open the form turns it into a quiet afternoon instead of a scramble against a deadline. studentaid.gov sets out whose information is needed in which circumstances.
A form submitted quickly with a wrong figure takes longer overall than one submitted carefully, because the correction has to be processed and the school has to see the updated version. Corrections are an ordinary part of the process and are free.
If something was wrong, fix it the same way you filed it. There is no penalty for a correction and no charge for one.
A good number of schools have an institutional aid application on top of the federal one, with its own earlier deadline. It is often the form that decides the school's own grants, which can be the largest non-repaid part of an offer.
Ask each school directly whether they have one and when it is due. It is not always prominent on their site.
Send it over. A person reads every message, and if the real answer belongs to your school's aid office we will say so.