The fruit tells a story about a person's character...

 Matthew 7:15-19 

Watch out for false prophets. They come to you in sheep’s clothing, but inwardly they are ferocious wolves. By their fruit you will recognize them. Do people pick grapes from thornbushes, or figs from thistles? Likewise, every good tree bears good fruit, but a bad tree bears bad fruit. A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire.

This was a warning given to the children of God to be very careful of false prophets (which we see these days). As described, some come wearing sheep skin pretending to be innocent and called to teach the word of God, only to find that they are there for their own agendas. This verse further tells us of how to tell which is which. This you will see by the fruits they bear, similar to fruit trees, you tell wat type of a tree it is by the fruit it bears. The apple tree will produce apples, an orange tree bears oranges. There's no way that an orange tree can bear apples (at times or all the time). It is the same principle with humans as well, the characters of people will tell you what type are they. Are the children of God or are they coming from the enemy camp.

How do we tell which fruit is which? Galatians 5:22 tells us of the fruits of the Spirit. Remember, Jesus left us with the Holy Spirit which lives in us. The same Spirit is the one that help mold us to be in a position to produce the fruits mentioned in this bible verse. This is what this verse says: "But the fruit of the Spirit is love, joy, peace, forbearance (patience), kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law." A person that exhibits these characters, you can believe that they are the children of Most High; obviously as guided by the Spirit. Remember the enemy also knows this information, and might try by all means to pretend to have such characters, but the question is for how long? That stunt will not last forever, one way or the other, it is bound to be revealed. 

The best way to assess a person, is by taking it to the Lord. He will never lie, He will guide you.