Based on Mishnah Torah I: Book of Knowledge, the Laws of Foundations of Torah, Ch. 10
The opening words of the Rambam ch. 10:
1) Any prophet who arises and tells us that God has sent him does not have to [prove himself by] performing wonders like those performed by Moses, our teacher, or like the wonders of Elijah or Elisha, which altered the natural order.
Rather, the sign of [the truth of his prophecy] will be the fulfillment of his prediction of future events, as [implied by Deuteronomy 18:21]: "How shall we recognize that a prophecy was not spoken by God?..."
Therefore, if a person whose [progress] in the service of God makes him worthy of prophecy arises [and claims to be a prophet] - if he does not intend to add [to] or diminish [the Torah], but rather to serve God through the mitzvot of the Torah - we do not tell him: "Split the sea for us, revive the dead, or the like, and then we will believe in you." Instead, we tell him, "If you are a prophet, tell us what will happen in the future." He makes his statements, and we wait to see whether [his "prophecy"] comes to fruition or not.
Should even a minute particular of his "prophecy" not materialize, he is surely a false prophet. If his entire prophecy materializes, we should consider him a true [prophet].
2) We should test him many times. If all of his statements prove true, he should be considered to be a true prophet, as [I Samuel 3:20] states concerning Samuel, "And all of Israel, from Dan to Beersheba, knew that Samuel had been proven to be a prophet unto God."