Just recently, I came to a new and simple understanding of the fact that God knows everything we are going to do and say before we ever do it. there are certain aspects of God's omniscience that I'm not even going to pretend to understand but there are other parts that may not be all that mysterious after all. the part that I am talking about is that part of us that is sinful and broken by nature.
I think it really is easier for God to predict us than we think in the same way that it is very easy to predict what a robot will do if you know what it is programmed to do. A robot will not operate outside of it's programming. In the same way, we are born with a programming that is broken and bent towards doing evil. We're robots with a really bad program and a really predictable pattern.
God has been around for a long time.....I would imagine that He knows exactly how every choice we make is going to play out. Even as original as we may think our decision making process is, God has been around for a long time....He knows where it's going with out having to "see in the future" (although He certainly has that ability as well). Even in our most inventive expression of sin, we're predictable. There's not much freedom in being predictable and there's not much wisdom in ignoring the only One who knows how it's all gonna play out...