Chemistry, Physics, Math, English are all easy classes to get into.
Biology classes are relatively ok when it comes to 93, 94, 97, 98, 99. You for sure won't get your choice of teacher, and you might even have to wait until you're a sophomore before you start just so you can get a head start when it comes to your registration date, but overall it's not so bad. Upper division classes are really hard to get into. These classes are often pretty much reserved for junior/senior bio majors, and even they don't really get their top choice. As a non-bio major you'll just have to grab up an empty seat in whichever random upper div class opens up. Upper division labs are closed to non-bio majors. This last block, as well as the other problems I just mentioned, are all easily avoidable if you take the classes over the summer, when plenty of seats are available and all restrictions are lifted.