As far as distinguishing what "voice" is from God and what is not . . . one of the big "A-ha!" moments for me in coming to Biblical Christianity was learning that feelings are not to be primarily trusted. I say "primarily" because, yes, it is true that the Spirit will at times impart a strong feeling or intuition to avoid something or to confirm something, but in general the Bible teaches that, "The human heart is the most deceitful of all things, and desperately wicked." --Jer. 17:9
One of the main things we come to realize in being reborn . . . is just how constantly sinful our "natural" (fallen) heart is. Many times, even when feeling compelled to do some "good" thing, even a "selfless" thing . . . if you dig a little within and look behind the curtain, you will find that really there again is just concealed pride, self-righteousness--a lurking ulterior motive, however subtle that is not actually so "selfless" afterall. . . .
We are in a desperate pickle here. . . . We are inclined to nothing truly good and the lengths to self-deception are stunning the more you progress in sanctification. You begin to realize just how utterly we need a Savior--to save us from ourselves. You also begin to honestly appreciate, with great thankfulness and humility, that if and whenever you DO do something "good" . . . it is not YOU who does it, but Christ--the Spirit--Who is in you. All glory, all credit go to Him.
A major temptation which most suffer from, also to be noted, is the feeling or belief that we ("I", "me") are meant to do something "special" and profound in this life, in this world. Here is where many go off the rails and claim to be "hearing from God" a unique "revelation" . . . and then proposing novel and new interpretations of scripture, which somehow nobody "saw" before. Before long, the would-be "prophet" is leaving the text of the Word, coming up with "new" instructions, fomenting a "following" and yes, the cult is soon to follow.
The simple, hard beauty of having the Bible--the Word of God--is that He HAS spoken to us, and He speaks to us through His Word. Which is why so many hundreds, thousands, have fought and suffered and died to preserve the Word, through the centuries . . . and why, as true Believer, the Book becomes increasingly so precious. If a person never gets a single "personal revelation" from God, it does not matter, because we have His living Word already revealed and kept for us to access any time we want and need it. And there IS a supernatural component, you will find, as the Spirit indwells you, that the Spirit teaches you, interacts with you, as you interact with His Word.
The great danger in considering the Bible casually or valid only "so far as translated correctly" . . . such as the Mormons do, is that there is no longer an anchor and test for truth. You can present a foot high stack of historical FACTS to the Mormon . . . about, for instance, the deceitful, perverse, con-man-like character of Joseph Smith . . . and the mountain of contradictions, un-Biblical teachings and occultish doctrine and sordid history of his church . . . and the Mormon will figuratively stick their fingers in their ears, shut their eyes, and say "I know the church is true, I know Joseph Smith was a true prophet etc." and you ask them how they know . . . and they usually will reply that their "feelings" confirm it--the proverbial "burning in the bosom".
But a person can get strong, emotional, "positive" "feelings" at a good rock concert, or from a poem, or at a movie or from a million different situations, none of which necessarily confirm the truth of the thing. Feelings are NOT to lead us to truth. Once saved, feelings may indeed follow, but they are like the weather and not to be relied on.
As far as "voices" or certain of that internal dialogue that goes on and on, you should know that the devil is real and demons are real and I would suggest that they are often quite busy in this area. One of their favorite tactics is to accuse--to recall to your mind all the mistakes and sins of the past and to tell you that God hates you and that you are not worthy to be loved by Him . . . you could never be forgiven . . . and to cause you to doubt that you are saved.
Again, the Word of God comes to the rescue, which is why it is called a "weapon" . . . "the word of God is alive and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow,"
In answering the accusatory spirit that hates you and does not want you to find the peace of the Lord, you can say, "tell me something I DON'T know! Of course I am unworthy! Yes, I HAVE sinned terribly against God. No, I don't deserve to be saved! Which is why I LOVE THE LORD, because He died for me while I was yet a sinner! JESUS is worthy! HIS righteousness, not mine, is why I get to be with God, perfected in HIM, HIS work!"
The Believer has abandoned trying to please or impress God with his own self and works. We rely on Jesus' character and works, which are perfect. The moment you are saved--when you repent and thereafter put your trust in the Lord, God the Father no longer sees your sins. Christ stands in your place as your advocate and there is nothing the devil can say or do to defeat Him. When He said "it is finished" . . . it was and is! This is what the Bible teaches and what we rely on.
Something else to know. . . . Oftentimes, though not always, it happens that when a lost soul is finally found and saved, there is a special grace period, where you will hear from God in a closer, stronger and more personal way than usual. This is to strengthen and confirm the "babe" in faith. This may happen, but you don't really want to be looking for it. It is a quiet, sort of private thing, between you and God and I think you will be able to clearly recognize it. Just know that He will not put thoughts or feelings in you which will contradict His Word. The Bible is always that anchor and the template against which to test all things. A lot of Christians kind of freak out when this grace period goes away, thinking that they have done something wrong, displeased God, or have lost their faith. While actually, it is simply a matter of . . . that the Spirit helps you in the beginning get your "sea legs" in the new Walk . . . but then, we are expected to mature and be able to weather things without that constant extra touchy-feely support. Not that He ever leaves, but the Spirit does seem to withdraw sometimes, where He is hard to detect, as we are encouraged to strengthen the FAITH side of our progress, continuing on faithfully, through those valley/desert/dark night moments.
Knowing His laws, His commands is enough to have, without extra or special communications "in the Spirit" . . . when we are in those times when the Spirit withdraws. Don't lie, don't covet, don't lust, don't cheat . . . and above all, which pulls all those commands into line, is to learn how to love others as yourself. Impossible, yes, in our natural self, but you can pray to God and ask Him for this ability and . . . in time . . . you will startle yourself as you find yourself reacting to others' annoyances or affronts . . . with real, supernatural even, compassion . . . and yes, love.
As you focus more and more on Him and His Word, you will find that the internal dialogue and suspicious whisperings within . . . you tend to ignore and slough off. They lose their poignancy and power and fade away. A shield of protection begins to develop around and in you, the more the Spirit abides in you (whether you feel that Spirit or not) . . . and a hunger and craving for righteousness sprouts and grows, so that all you want is more of Him and anything to do with Him and His work in this fallen world. . . . Key to ALL discernment, which ARE commanded to practice, along with judgment . . . is to test what is heard, felt, intuited etc. against what He speaks to us in His Word. Everything we need . . . to conduct our life, our choices . . . is found there. It is the treasure of all treasures!