Early voting gets underway Monday for Georgia’s May 20 primary election, giving voters a say on GOP challenges to Republican Gov. Nathan Deal, contested races in both parties for Congress, as well as state and local races.

As this year’s election season opens, here’s a reminder about how the state’s primary system works and how to find out where to vote:

WHERE DO I VOTE?

Any voter registered in Georgia can vote early. Voters can see personalized sample ballots, verify their registration status and find early-voting polling locations on the secretary of state's "My Voter Page" website (www.mvp.sos.ga.gov). It's important to check because a regular neighborhood polling place may not be open; often, local municipalities only open select sites during the 21-day early-voting period.

Information about local elections can also be found on the state's new "GA Votes" mobile apps. You can download the free apps for both Apple and Android operating systems using either the iTunes app store for an iPhone or iPad or Google Play for Android.

WHAT TO BRING WITH YOU

Georgia requires voters to show photo identification when they vote in person. Approved forms of identification include a Georgia driver’s license, even if it’s expired; a state-issued voter identification card; a valid U.S. passport; and a valid U.S. military photo ID.

PICK A BALLOT

Because the state conducts an “open” primary, voters may vote on a ballot of any party — you make your choice at the polls or when asking for an absentee ballot. You cannot, however, vote in more than one party’s primary.

So, once you pick a ballot, you have to stick with that same political party even if there is a runoff (in other words, you can’t cast a Republican ballot in the main primary but then vote in a Democratic runoff).

RUNOFFS

A number of races this year have more than two candidates, making runoff elections possible. That’s because Georgia requires election winners to receive more than 50 percent of the vote — you’ll often hear politicos refer to this margin as “50 percent plus one (vote).”

Georgia’s primary runoff this year is scheduled for July 22. Winners will move on to the Nov. 4 general election.