Start at the end, rather than the beginning. In other words, start with yourself and work backward. This will assure that you are indeed working with your ancestors, and not someone with the same or similar surname. Family names are spelled in differing ways from generation to generation. There is no "correct" spelling for any name.

Record everything you know
About each of your parents, grandparents, great grandparents, etc.: Birth date, Birthplace, Death Date & Burial Location, Names, and data on all their children, Marriages, Education, Immigration and naturalization, Military Service
Careers, Awards, and so forth.

Verify All Information
Even though it may be in print, or on a CD-ROM, it still may be incorrect. Transcription errors are common. Some records are even fictionalized. All facts must be verified. Record details of  all information sources.

Record your information on standard genealogical forms, such as Pedigree Charts and Family Group Sheets. These forms can be obtained from your local genealogical society, stores specializing in genealogical supplies, and downloaded from various sites on the Internet. Genealogy software programs can generate blank forms.