Free will plays an integral part in the Christian faith.
God didn't want for Adam and Eve to partake of the fruit of knowledge of good and evil, (thus telling them not to), but because of free will, Adam and Eve deliberately chose to disobey God. God didn't intend for this to happen, but He knew it would. Wait, if He knew it would happen, why did he bother putting the tree there at all? Couldn't He have anticipated and preempted man's actions somehow? Yes, but to do so would negate the need for free will, which had been bestowed upon man because God loved us enough to allow us to choose whether or not to love Him, because ultimately whatever choice we make, it wouldn't make a difference. I wrote a bit on this a while back.
Have you ever wondered what it'd be like if Jesus backed out of being crucified? If he had simply denied everything and gone his own way? Where would that leave us?
What if I had never met my wife? What if I were in that earthquake? Was it meant to be, or was it pure coincidence?
In certain instances, God knew exactly what would happen and used this knowledge for his purposes, for example, with Moses and Pharaoh.
This is not to say that 'if I ended up smoking, then God would've known so this must all be part of His plan.'
The concept of predestination leads people to believe that Christians are meant to be Christians, and non-Christians were just never meant to go to heaven. I think that's wrong.
Let's call Heaven dry. And Hell wet. If one wishes to stay dry, then one shouldn't jump in the pool. If one wishes to be wet, then in the pool one goes. The water in the pool is inherently wet. There's nothing we can do to change that. But whether or not we choose to jump in is the deciding factor in whether we stay dry or get wet.
God could make the stars align forming the initials of your name and appear in a pillar of fire and speak to you saying: 'I am the Lord', but whether you choose to believe is entirely up to you. God has a plan, but ultimately, your determine your fate.