Decide how much extra money you need. Draw up a profile of your family finances and see how far short you fall on paying for the education you want. You'll need this information when you finally apply.
Do some online research. The federal Department of Education offers advice on applying for federal grants on its website, along with links to state programs and downloadable application forms.
Check out any special state or federal programs that offer grants based on poverty levels, veteran status, career plans or other factors other than pure financial need.
Go over, in detail, the application for any grant you want. Make sure you know exactly what will be required, whether you can meet the standards and how much money you can expect.
Ask for help applying if you need it. Writing grant applications can be challenging enough that there are professionals who devote themselves to it. There are also books that will instruct you in grant writing for a lesser cost.