Question:
How can one be sure they are not interpreting the Bible correctly?

Answer:
One way that this will become evident is by running into verses that seem to contradict each other. For example, let’s say that you believe that Mark 16:15, 16 (“Go ye into all the world, and preach the gospel to every creature. He that believeth and is baptized shall be saved; but he that believeth not shall be damned.”) is teaching you that BAPTISM IS NECESSARY TO BE SAVED. Then you run into 1 Corinthians 1:17, 18, which reads, “For Christ sent me NOT TO BAPTIZE, but to preach the
gospel…for the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.”
These two passages seem to contradict each other because of your belief that Mark 16:16 is teaching the necessity of water baptism, but in reality your interpretation of Mark is wrong. Mark states emphatically, “He that BELIEVETH NOT shall be damned,” thus it is the lack of faith, not baptism, which damns the soul. Believing the gospel is the only necessity for salvation, as 1 Corinthians 1:21 goes on to say, “…it pleased God by the foolishness of preaching [the gospel] to SAVE THEM THAT BELIEVE.”
When one makes such a discovery, they must then rely on the Spirit of God (Who alone can give us the true interpretation for any Scripture—1 Corinthians 2:9-13) to reveal to them the true interpretation of the Scripture which is not clear. (In the case above, they would want to know why baptism is mentioned in Mark 16:16 when it is not necessary for salvation.) And we must remember that “Scripture interprets Scripture'” that is, we can only learn what one Scripture means by comparing it with other Scriptures. Second Peter 1:20 reads, “Knowing this first, that no prophecy of the Scripture is of any private interpretation.” This is telling us that in interpreting prophecy, prophecy must be taken as a whole by comparing prophetic Scriptures with other prophetic Scriptures. But in principle this is true of the whole Bible—no verse should be interpreted by itself, but in the light of the context and of all the rest of Scripture.