You will know them by their fruits

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Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves. Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?
Matthew 7:15-16

There is no doubt that many false prophets and teachers have taken advantage of  people. They succeeded by hiding their real intentions in their quest to satisfy their greed. They come in sheep's clothing hence you do not usually suspect them. They play on emotions as they try to captivate their audience. This has somehow made it difficult for those who genuinely care for the sheep but not impossible.

We can distinguish the false prophets from the true prophets by their fruits. The false prophets being ravenous will always bear fruits of greed. Don't be impressed with their charisma, look for character. Who preachers are is the main thing not what  they say. A genuine leader will never exploit your emotions or your pocket. There are no friendly wolves among sheep.

Jesus also mentioned two popular fruits of their times- grapes and figs. Since the people were mostly farmers by trade, they could understand this metaphor. The teaching and character of any true prophets will be consistent.  When you hear someone telling you to gather grapes from thornbushes or figs from thistles then you know you should run from them. You cannot gather grapes from thorns or figs from thistles.