First, we have to understand WHAT is Predestined. It is, that from before the foundation of the world, God loved what He was going to create, mankind…(us!) Then He created it, and loved it all the more. He Predetermined or Predestined that those who would choose Faith in Jesus Christ would be saved for eternity.
Why? Because He knew that The Fall would happen and that man would need a Savior, so from before the beginning He made a way, through Christ Jesus, His death-payment for our sins! Jesus Christ is, remember, the Jewish Messiah, so those “before” Christ who believed in the coming of their Messiah would be … saved.
Man was given Free Will to choose, because man is not a robot. The very best gift a Father can receive is the Love he gets from his children! So if man did not have free will to love God then God would not really be loved at all!
So, please, see that it was the Plan of God that was Predestined, not the specific choices of specific persons, and as such that the Free Will of man is true also.
The larger question, really, might be “How does a man choose God?” What does a man do to “choose” Jesus Christ as his personal Savior? Is it “belief” in Christ? Is it “following Christ”? Is it “faith in Christ”? Obedience? Sacrifice? Love? And, how is it that a man’s choice is measured or determined? What is the proof of it? These things are worth our serious consideration.