The most important advice I can give you is to keep your eyes on Christ, and not let yourself be turned away from Him. Satan will do everything he can to turn you away from Christ, but don't give in to his pressures. God's Word says, "I have no greater joy than to hear that my children are walking in the truth" (3 John 1:4).
In what ways might your faith be attacked? One way, of course, will be by those who don't believe in Christ, and may actually mock the Gospel or attack it. And this won't happen only in the classroom; some of your fellow students may be even more scornful of the Gospel than the occasional atheistic professor. But even if you can't answer all their questions, they aren't the first ones to raise them, and scholarly Christians have provided answers. Your local Christian bookstore can help you find them.
But I find that many students who have come from a Christian background turn their backs on Christ in college not because of some intellectual challenge to their faith, but because of social pressure the pressure to live like everyone else.
Don't let this happen to you, but ask God to lead you to other Christians on your campus who can encourage you and be your friends. The Bible says, "Flee the evil desires of youth, and pursue righteousness, faith, love and peace, along with those who call on the Lord out of a pure heart" (2 Timothy 2:22).