It's very important to check maps. Boundaries change over time. Be sure the area where you think your ancestors resided is actually the area where they were.
Y chromosome: One of the two sex chromosomes, X and Y. The Y chromosome passes down from father to son. Females do not receive it. As the Y chromosome is passed on through the paternal line, it is valuable for surname based genealogy studies.
Probate records are often overlooked in some family histories. Sometimes they can bring down your research brick wall. They may show relationships, financial status and life stories of your ancestors.
When looking at deed indexes, be sure to look at both the "Grantor Index", an index to those selling the land and the "Grantee Index", an index to those buying the land.
The Family Group Sheet identifies a couple and their children. Everyone with a spouse or child has two group sheets; one as a child with parents and usually one as a parent with children.