How do we know if a church teaches sound doctrine?

Sound doctrine is that which conforms to the teachings delivered by Christ and His apostles, as pointed out in 2 John 1:9 and 1 Timothy 1:3. This includes not only proper understanding of the gospel but also the correct administration of ordinances like baptism and the Lord's Supper. A church that deviates from this faith or incorporates false teachings is not regarded as a true church of Christ. As believers, we are encouraged to test teachings against scripture to ensure they align with sound doctrine.