Any advice on what to expect or how to prepare for college auditions?
Plus, what are some pieces I should be familiar with ahead of time?

Thank you!

It depends on where you are looking at auditioning? What schools are you interested in?

practice practice practice...brahms sonatas, mozart concerto, weber concerto. I am afraid if you are asking this question you need to change clarinet instructors....cheers

I can tell you that professors will have heard a LOT of uneven, uncontrolled playing. If you want to sound like a good bet for a college jury, make sure you have control of your tone/timbre in all ranges and evenness of technique. For example, in the Mozart Clarinet Concerto, you should (as an aspiring college entrant) make the rhythms match a computer playing the piece. Play the Debussy Premiere Rhapsodie and make sure all the 32nd note passages are very controlled and clear so that every note can be heard (too many young people play them as a "rip" and just throw the notes in).

Try this document to help with evenness of technique. https://drive.google.com/file/d/0Bzsgx9rbeeEyY2RhRXpIbTdaTWs/view?usp=sharing