This Saturday, December 14th, there is a run-off election in Houston (and perhaps other places) If you live in Harris County (TX), you can find out if you have a run-off election in which you need to vote, as well as where to find your polling place and ID requirements.
In Harris County (TX), you can go to HarrisVotes.com. Other places have similar sites. If you don’t know if you have an election or where to get info, the best place to found out is your Secretary of State (SoS). If you don’t know the URL of your SoS, you can search with quotation marks as written: “secretary of state” [your State]
Vote and good luck!