Just as you can identify a tree by its fruit, you can also identify people by their actions (Matt. 7:20). The Holy Spirit produces good fruit in our lives; the lives of true believers. All verses come from the KJV Bible.
Some traits true believers display (those that follow the urgings of the spirit, they produce good fruit):
Galatians 5:22 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith,
Galatians 5:23 Meekness, temperance: against such there is no law.
Two more primary marks of a true believer are continuation in Christ’s word (obedience, see John 8:31); and chastening by the Lord of the true believer (in other words, there will be discipline, correction, etc. when necessary; kiss the paddle and move on).
Some desires of true believers: To please God, to do His will, not their own will; to know God's word by studying that word, they truly seek Him; to be with God's people [assemble, fellowship] when possible; to share the Gospel with those that need it; to overcome sin; to be a good example for others in the hope of them seeing what you have and wanting it too.
Some traits that unbelievers display (those that do works of the flesh, bad fruit):
Galatians 5:19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
Galatians 5:20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
Galatians 5:21 Envyings, murders, drunkenness, revelings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
2 Timothy 3:3 Without natural affection, trucebreakers, false accusers, incontinent, fierce, despisers of those that are good. (They will be unloving and unforgiving; they will slander others and have no self-control. They will be cruel and hate what is good. Sound familiar)
2 Timothy 3:4 Traitors, heady, highminded, lovers of pleasures more than lovers of God. (They will betray their friends, be reckless, be puffed up with pride, and love pleasure rather than God).
2 Timothy 3:5 Having a form of godliness, but denying the power thereof: from such turn away. (They act holy or claim to be a preacher of God, but reject the power that could make them Godly. Never teaching the truth of the Word, but cling to traditions of men. Run from them, don't associate with them).
Become a fruit inspector, not a judge. God is our one and only judge.
Food for thought: Do you see any of the above unbeliever traits today in 2022? All you have to do is watch the daily news, read a newspaper or observe with your own eyes.
Why did Jesus come? Matthew 9:10-13; Mark 2:16-17; Luke 5:30-32; these verses tell you. Is there a better example?
Is this a complete description of true believers and unbelievers? No, but the Bible is. Read and study for yourself. Don't trust me or any other man, trust God.
What you believe will determine how you live.