This is another topic where it’s rather presumptuous for a nontheologian to weigh in at all, but let me reassure the reader that in my humble opinion this is also another issue where it’s a mistake to agonize over reaching a definitive resolution: Clearly there will never be such a resolution, and since we might have free will, then shouldn’t we play it safe and assume that we ought to exercise it rightly?
Anyway, to state briefly the problem: How can we have free will if God is omniscient? And here are some possible answers: (a) Right, we can’t (but see preceding paragraph). (b) God is outside of time (on this point, by the way, see C.S. Lewis’s reference to Boethius in the twenty-seventh of The Screwtape Letters). (c) Since God can do anything, he can give us free will and thus abdicate some of His omniscience. (d) The Bible’s (and, through it, God’s) repeated exhortations for us to behave ourselves make no sense if there is no free will and all is predestined; if, then, as Christians, we accept the truth of the Bible, then we should not try too hard to figure out how we can have free will — we just have to assume that apparently we have it, or at least that we might have it, and exercise it rightly (the same conclusion reached in the first paragraph here, by a slightly different route).