True belief in Jesus Christ is to do the works that Jesus asks us to do. You go out and murder, steal, commit adultery, etc and then claim that you believed in Jesus Christ will not bring you salvation. Repentance and believing in Jesus enough to follow his teachings is true belief or true faith. Like the Apostle James declared:
James 2:14-26
14 What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him?
15 If a brother or sister be naked, and destitute of daily food,
16 And one of you say unto them, Depart in peace, be ye warmed and filled; notwithstanding ye give them not those things which are needful to the body; what doth it profit?
17 Even so faith, if it hath not works, is dead, being alone.
18 Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.
19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
20 But wilt thou know, O vain man, that faith without works is dead?
21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
22 Seest thou how faith wrought with his works, and by works was faith made perfect?
23 And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
24 Ye see then how that by works a man is justified, and not by faith only.
25 Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent them out another way?
26 For as the body without the spirit is dead, so faith without works is dead also.
Although it is not the works, in and of themselves, that save us but that they are required by the Lord before he will grant his saving grace upon us.
Matthew 7:21
21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
