Time lines are really great visuals that help to show the events that have been documented in your ancestor's life. They also reveal the time period in your ancestor's life when you are missing documentation. When you identify these holes in your research, you can work to locate resources that cover that time period if they exist.
You can easily see if you have been able to document a birth, marriage or death record, and then you can reference the time line to be sure to check for other records. For example, I have been very successful with helping others to link to the generation back by using the Family Group Sheet to identify the siblings of an ancestor. After the each sibling has been accounted for, you can search for possible death certificates for each one. Death certificates often reveal the names of parents names and birth places if known. I have multiple death certificates on siblings naming the same parents, providing the place of birth for the parent, and giving the surname of the mother. This is a vital principle if there is no other conceivable way of establishing parentage.
The above is a FamilySearch Timeline. You may also create one using the Biographical Outline at FamilyTree Magazine:Click here. Be sure to keep your time line up to date as you discover more resources.