Start with what the church believes
Read the church's statement of faith and denomination or tradition. You do not need to understand every theological term immediately, but you should be able to tell whether its core teaching is recognizably Christian and whether major beliefs fit what you are looking for.
Listen to the teaching in context
One sermon can be unusually strong or unusually weak. Listen to more than one if possible. Notice whether Scripture is handled carefully, whether difficult passages are explained honestly and whether the teaching points toward Christian life rather than personality or hype.
Watch how people treat each other
Community is more than a friendly greeting at the door. Look for signs that people of different ages and backgrounds can belong, that leaders are accountable and that there are healthy ways to ask questions or receive help.
Consider whether you can realistically participate
A church that is excellent but impossible for you to reach consistently may not become your church. Location, service time, transportation, family needs and accessibility all affect whether community can become a habit.
Give a promising church more than one visit
Unless something is clearly unsafe or deeply concerning, consider attending several times. The room becomes less foreign, you hear more teaching and you can see whether relationships and service opportunities are real.