Write it down carefully, documenting who said it, their phone number, address and date. Don't rely on word of mouth, DO send for the actual birth, marriage, death certificates so you can arrive at a consensus of fact. Their job is to guide you so you can begin an effective discovery of your heritage. The same steps are universal to genealogy. Learn and do them before you do ANY genealogy.
Most people choose a relative at the place where their family line ends.
Begin with yourself and write down your name, birth date, place of birth, marriage if applicable, children, etc. Next, fill in the blanks below concerning you father. If you do not know the information, then look through family papers. You may have to send for a birth or death certificate to verify the facts. Now, see if any of your relatives has information on your great grandparents.