First find your grandmother on the census with her siblings and parents. If you are very young, you might have to start with her parents instead. Trace that person back through all the censuses to their birth. If you have trouble with maiden names, try to get the marriage certificate or record based on the male's surname and the woman's given name. Keep working backwards in time. Record all the siblings as you go back in time. That is one way to help identify that a family in census A is the same as in Census B if they moved. Yes siblings are born, marry or die but you will see a progression.
Each step of the way back get death, marriage, and birth certificates for your direct ancestors until you are far enough back they don't exist. Note these records are usually not on line and must be ordered from the government body that holds them, sometimes the county, sometimes consolidated at the state level.
When you get back before the formal records, counties often had ledger books recording births, and especially marriages and deaths. So check FamilySearch.org, visit county courthouses if you can, contact county historical societies.
There are 10 times as many records NOT on the internet as you will ever find on the internet.