If your grandparents, like mine, were born before birth certificates, ask what they used instead. You can either draw your own and xerox them, or buy from a genealogy supply outlet. First, a pedigree chart. You are number 1, or, if you prefer, you and your spouse are 2 and 3. Other than number 1, even numbers are males, odd numbers are females.
Print names out in full, and record women by their maiden names.
Second, a family group sheet. On this goes father, mother, his other wives, her other husbands, their parents, and all their children and their children's spouses. Next, with partially filled out forms in hand, talk to your older relatives. Usually someone in the family is interested in family history. Most older people are happy to help when younger relatives show interest in the family.