Sorry for the long post, but I wanted to post the Scriptures as you asked:
You must repent to be saved:
Ezek 18:30b Repent, and turn yourselves from all your transgressions; so iniquity shall not be your ruin.
Luke 5:32 I came not to call the righteous, but sinners to repentance.
Luke 13:3b and 5b except ye repent, ye shall all likewise perish.
Luke 15:7 and 10 I say unto you, that likewise joy shall be in heaven over one sinner that repenteth, more than over ninety and nine just persons, which need no repentance...Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth.
Acts 3:19a Repent ye therefore, and be converted, that your sins may be blotted out
Acts 17:30b God...now commandeth all men every where to repent
Acts 20:20-21 I...have taught you publickly, and from house to house, Testifying both to the Jews, and also to the Greeks, repentance toward God, and faith toward our Lord Jesus Christ.
Acts 26:19-20 I was not disobedient unto the heavenly vision: But shewed first unto them of Damascus, and at Jerusalem, and throughout all the coasts of Judaea, and then to the Gentiles, that they should repent and turn to God
Repentance must be granted by God, though:
John 6:65 And he said, Therefore said I unto you, that no man can come unto me, except it were given unto him of my Father.
Acts 11:18b Then hath God also to the Gentiles granted repentance unto life.
2 Tim 2:25b if God peradventure will give them repentance to the acknowledging of the truth
I think Paris Reidhead says it best to not try to figure out the "why" that is stated in Scripture, but rather just understand the "that" stated in Scripture.
We should preach, we should pray, God bringing the increase. Anyone who claims to understand grace worked in the heart by the Holy Ghost to 100% accuracy is either much more intimate with God than everyone on this site, or they are just guessing.
God chooses who are His:
John 15:16 Ye have not chosen me, but I have chosen you, and ordained you
...then He draws them:
John 6:44 No man can come to me, except the Father which hath sent me draw him
...through the preaching of repentance and the cross:
Luke 24:47 repentance and remission of sins should be preached in his name among all nations
But clearly the Holy Ghost can be resisted:
Acts 7:51b ye do always resist the Holy Ghost: as your fathers did, so do ye.
This does not discount the foreknowledge and predestination of God's elect:
Eph 1:11 In whom also we have obtained an inheritance, being predestinated according to the purpose of him who worketh all things after the counsel of his own will
Nor does it discount the freedom we are given to reject God:
Rom 1:24 and 26 Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves:
For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
So my take on all this is that God sovereignly chooses a man (John 15:16), but the man is free to resist the Holy Ghost (Acts 7:51). But God has knowledge of everything that will come to pass ahead of time. If the decision was 100% God's and nothing of ours, why would there be a judgment? If the decision was 100% ours, and nothing of God's, you have a God that is not in control.
God always does His part, if man chooses not to do His, and accept the free invitation into God's family, he will burn for eternity. But the Father is not anxious, neither was Christ during His ministry because:
2 Tim 2:19a Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his.
Concerning who will be numbered with the saved /lost: He knows, we don't.
Spurgeon put it best (paraphrased), when he said, 'God call out your elect. And then elect some more.' As well as, 'On the gates of heaven, we will see the words "whosoever will." But then, looking back after passing through, will see "the elect of God" on the inside.'