Matthew 7
Jesus gives us a standard for judgement.  The standard is this:  How you judge others = how you are judged.  If you judge harshly, you will be harshly judged. If you show mercy, then you will receive mercy.  However you treat others, be sure that it is how you want to be treated.
So, how should we act?
We must always check our own hearts and motives and attitudes first.  We must take care of our own "eye"  beams.
Psalm 51 gives a great prayer model for doing just that.
"Be gracious to me, O God, according to Thy lovingkindness; according to the greatness of Thy compassion blot out my transgressions."   Eye beams / sins that keep us from seeing correctly must be removed by our loving and kind Father in Heaven.  We must humble ourselves and come to Him seeking His mercy and grace.
"Wash me thoroughly from my iniquity and cleanse me from my sin. For I know my transgressions and my sin is ever before me.  Against Thee, Thee only, I have sinned, and done what is evil in Thy sight, so that Thou art justified when Thou dost speak, and blameless when Thou dost judge."  ( v2-4)
We must not only notice the beam in our own eye.  We must agree with God that we are sinners, confess those sins, confess our need for His forgiveness and cleansing.  We must admit that God is Right and we are not, that He is Judge and we are not.
"Behold, Thou dost desire truth in the innermost being, and in the hidden part Thou will make me know wisdom."
Jesus tells us in Matthew 7, that the wise man builds his house on the rock.  That is the man who not only hears what Jesus says, but acts on them.  He requires genuine repentance.  It is a small gate and a narrow way "that leads to life".   Not many go that way.   In fact there are so many that are wolves  in sheep's clothing that Jesus gives us a way of judging correctly.  Even judging ourselves correctly!
We will "know them by their fruits" ( Matthew 7:20).   Only if the fruit is good do we know that the tree is good.   Only those who are doing the will of the Father will enter the kingdom. Only those who hear His Words and act on them will survive.   That is the narrow way.
The psalmist prays "Create in me a clean heart, O God, and renew a steadfast spirit within me." 
( v10)
He prays for the Holy Spirit.  For the joy of salvation.  For a willing spirit. He prays for good fruit.
The fruit of the Spirit, Paul tells us, " is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control;"  The psalmist tells us that these do not come by burnt offerings and sacrifices, but by a "broken spirit; a broken and contrite heart".
There were some who said "Lord, Lord".  Who had great credentials - They prophesied, they cast out demons, they performed miracles.  But they didn't know Jesus as their Savior and Lord.  They never entered the narrow gate.  Never confessed their sins, never removed their eye beams, never did the will of the Father.  Never had any "good" fruit.

How then, can we know this narrow way, how can we bear good fruit?
Pray, Jesus tells us.
Ask. Seek. Knock.  Keep asking.  Keep seeking. Keep knocking.
Our Father in Heaven is the giver of what is "Good".   He gives us the Holy Spirit, Who leads us into all righteousness.  It is daily asking.  Daily seeking. Daily knocking... and daily receiving life from Him.
Jesus tells His disciples, "I am the true Vine and My Father is the vinedresser. Every branch in Me that does not bear fruit, He takes away; and every branch that bears fruit, He prunes it, that it may bear more fruit..... Abide in Me and I in you, As the branch cannot bear fruit of itself unless it abides in the vine, so neither can you, unless you abide in Me." ( John 15:1-2,4)

Precious Savior, thank You for the Truth of Your Word that cleanses us as we walk in it.  Break our hearts before the Father, that we might confess all sin and find the joy of Your salvation.  Create in us clean hearts and steadfast spirits.  May all beams be removed from our eyes.  May our lives be filled with good fruit. To the glory of Our Father in Heaven.  Amen.