Start with yourself. Write down information about yourself that you want your children and grandchildren to remember! Then, add your children to a Family Group Sheet.
http://helpdesk.rootsweb.com/get_started/charts/FamilyGroupRecord.pdf
Make sure that you add everything you want your grandchildren to know about your children--remember this is a Family History Project!
Then go on to your parents, and begin an Ancestor Tree.
http://helpdesk.rootsweb.com/get_started/charts/AncestralChart.pdf
Again, write down everything that matters to your family history. Rootsweb.com has an excellent help guide to get you started.