Q.  How do you know what is "truth?”

A.  You have posed a good question.  Pilate asked the Savior the same thing in John 18:38.  With so many denominations and contradictory teachings, many do not know where to look for truth, and what to believe.
            First, we must believe and have faith that Yahweh exists.  “But without faith [it is] impossible to please [Him]: for he that comes to Yahweh must believe that He is, and [that] He is a rewarder of them that diligently seek Him.” (Heb. 11:6)
            The fact that you said that you watch many Sunday morning TV religionists reveals your spiritual thirst for truth or you would have no interest at all in things spiritual.
            This thirst, we understand, is the calling that comes only from Yahweh.  Yahshua said, “No man can come to me, except the Father which has sent me draw him…Every man therefore that has heard, and has learned of the Father, comes unto me.” (John 6:44-45)
            Yahweh calls those who He knows will grasp truth.  Yahshua then does the choosing.  He chose His 12 disciples: “Yahshua answered them, ‘Have not I chosen you twelve, and one of you is a devil?” (John 6:70)
            Only through Yahshua do we have the assurance of salvation: “Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved” (Acts 4:12).
            His Name Yahshua—given by the angel to His mother Miriam—means “salvation of Yah” (contraction of “Yah-Hoshua”).
            Therefore the first truth that we know demands that we call on the only Name that means and gives salvation.
            Take special note that Yahshua said every man must first learn of the Father.  The salvation plan the Father has for His people is called the Covenant, which He made solely with Israel.  In this Covenant (an agreement), Yahweh promised that He would protect and bless Israel (Ex. 23).  In turn, Israel exclusively would obey Him by keeping His laws and judgments.
            Israel, then, is key to Yahweh’s Covenant and His dealings with mankind.  The adoption as Yahweh’s sons and daughters, receiving the promises, having glorified bodies, teaching others of His law, and being with Yahweh—are all given to Israel.
            Isaiah 24:5 says that Israel broke the “everlasting” Covenant, however.  Instead of abolishing His plan, Yahweh now turns to mankind generally, to be grafted into His Covenant—this Abrahamic tree of promise—to replace the wayward Israelites.”  And if some of the branches to be broken off, and you, being a wild olive tree, were grafted in among them, and with them partake of the root, and fatness of the olive tree.” (Rom. 11:17)
            We are the new Israelites who must also adhere to the Covenant agreement of obedience to Yahweh’s law in order for the promise of salvation to be ours.  Notice, Paul says of his brethren “who are Israelites; to whom pertains the adoption, and the glory, and the covenants, and the giving of the law, and the service [of Yahweh], and the promises.” (Rom. 9:4)
            Yahweh has a program to save His people Israel: “And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away unrighteouness from Jacob.” (Rom. 11:26)  The only way we can inherit the promises is through Yahshua the Messiah; “And if you [be] Messiah’s, then are you Abraham’s seed, and heirs according to the promise.” (Gal. 3:29)
            Churches erroneously teach that Yahweh has given up on the Jews and Israelites and now He is working with the “church.”
            The truth is, Yahweh today is calling out a people to replace the branches He has broken off (the fleshly Israelites), which will allow the olive tree to bear fruit, Romans 11:17-24.  It is up to the called-out ones to accept or reject His Covenant, which is now placed in our hearts and minds:
            “For this is the covenant that I will make with the house of Israel after those days, says Yahweh; I will put my laws into their mind, and write them in their hearts: and I will be to them an Elohim, and they shall be to me a people” (Heb. 8:10).
            He is calling out a people now to become spiritual Israelites, to take the place of stiff-necked, rebellious, fleshly Israelites who refused to walk in His laws.
            The truth is, Yahweh is still working with Abraham’s seed.  Sincere believers and followers of Yahshua are today called Israelites: “And as many as walk according to this rule, peace be on them, and mercy, and upon the Israel of Yahweh.” (Gal. 6:16)
            It is up to you and me today to learn Yahweh’s law so that we may obtain the promise first given to Israel and teach Yahweh’s ways to other both now and in the Kingdom.  Those awarded everlasting life will be teaching the twelve tribes of Israel: “And Yahshua said unto them, Verily I say unto you, That you which have followed Me, in the regeneration when the Son of man shall sit in the throne of His glory, you also shall sit upon twelve thrones, judging the twelve tribes of Israel” (Mat. 19:28).
            Ezekiel chapter 38 onward tells of the coming Millennium in which Israel shall be brought back to Palestine.  Israel will again be restored to the land and a Temple will be built there and worship reinstituted.
            They will be taught by those who are learning Yahweh’s way of life here and now: “And has made us unto our Elohim kinds and priests: and we shall reign on the earth” (Rev. 5:10).  “Blessed and holy is he that has part in the first resurrection: on such the second death has no power, but they shall be priests of Yahweh and of Messiah, and shall reign with Him a thousand years” (Rev. 20:6).
            Those who lack an understanding of the Covenant promise established in the Old Testament may find this foundational truth quite different from anything they have heard.   Churchianity does not teach it, but provides a superficial explanation of the Scriptures that only skims the surface and suffers from incongruities, inconsistencies, and gaping holes.
            You cannot ignore two-thirds of the Bible (Old Testament) and think you have the truth.  Paul tells us in 1Corinthians 10 that what happened with Israel is for our understanding (v.11).  Furthermore he wrote of the importance of the Old Testament, “All scripture is given by inspiration of Elohim, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of Elohim may be perfect, thoroughly furnished unto all good works.”  You cannot understand the New Covenant without a clear comprehension of the Old, because the New Covenant is linked to the Old.
            This is a bare-bones sketch, but from your comments it strikes us that you are already aware of what we have written so far.  We teach the harmony of all the Scriptures into a continuing plan of the Creator for His people.
            In your search for truth there are several other verities you should look for.
            *The Sign.  The true Assembly teaches the sign that Yahweh has given to mankind that we might know Him: “Moreover also I gave them My Sabbaths, to be a sign between Me and them, that they might know that I [am] Yahweh that sanctify them” (Ezek. 20:12).  “And hallow My Sabbaths; and they shall be a sign between Me and you, that you may know that I am Yahweh your Elohim” (Ezek. 20:20).
            *The Seal.  You should be certain you are sealed with the seal of His correct Name with which His people are to be sealed before the winds of strife are loosed at the end of the age: “Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our Elohim in their foreheads” (Rev. 7:3).
            The seal of Yahweh is the Name of the Heavenly Father and the Son in your mind where use is both natural and automatic: “And I looked, and, lo, a Lamb stood on the mount Sion, and with Him an hundred forty [and] four thousand, having his [name and His] Father’s name written in their foreheads” (Rev. 14:1).
            We are sealed with His Name when we are baptized into the saving Name of Yahshua the Messiah.  We are then given His Spirit as a guarantee of the future.  “Who has also sealed us, and given the earnest of the Spirit in our hearts” (2Cor. 1:22; Eph. 1:13).
            Certain characteristics are also evident in Yahweh’s true assembly.  There the fruits of the spirit are manifest, Galatians 5:22, including agape love, John 13:35.  His saints demonstrate the traits of the one pure Philadelphia Assembly in Revelation 3, whose works He knows: they keep His Word and do not deny His Name, verse 8.  Yahweh is His Name!