Believe it or not, today there are "Prophet Schools" with people collecting money in order to "teach" or "train" us to become prophets - and many are willing to shell out money to these scheisters! A gift from God is a gift from God, and no human training or education can change that fact.
It seems in biblical times, there were actually prophet "guilds" - people who felt they had the gift, and got together to discuss their various prophecies (I Sam. 19:19-20, II Kings 2:3, 2:5, 4:38, and 6:1).
But, prophets who were actually used by Yahweh in those times were appointed by Him through divine revelation (Num. 12:6), and were inspired to speak for God (II Pet. 1:21). Once they announced that Yahweh had revealed their "Prophet of God" status to them, they were granted special privileges, such as not having to work a "regular" job.
To weed out any false prophets (those claiming to be prophets when God had not actually called them - Ezek. 13:3, Jer. 23:16), the Levitical priests would record every word a prophet spoke for the Yahweh (II Sam. 23:2). The prophecies recorded were for the immediate future (days, weeks), the near distant future (months, years), and the long-term future (centuries, millenniums).
As mentioned above, if a prophet ever spoke a single word for the Yahweh that didn't come true, all his writings were destroyed and he was killed.
Deuteronomy 18: 20 "'But if a prophet presumptuously speaks a word in my name which I didn't order him to say, or if he speaks in the name of other gods, then that prophet must die.' 21 You may be wondering, 'How are we to know if a word has not been spoken by ADONAI?' 22 When a prophet speaks in the name of ADONAI, and the prediction does not come true -that is, the word is not fulfilled -then ADONAI did not speak that word. The prophet who said it spoke presumptuously; you have nothing to fear from him.
YHWH makes no mistakes. Isaiah, Jeremiah, Daniel, Ezekiel, etc., all lived their whole lives, uttering 100% accurate prophecies; therefore their writings were preserved. Today, there are many who believe themselves to have "the gift of prophecy"; but, in fact, their "prophecies" are nothing more than things they've conjured up in their own minds. One must therefore always make sure that all "prophecies" line up perfectly with the Bible. If they don't, then they aren't from God! Please see our Exposing false teachers and prophets page.