Knowing your way around a PC and Mac operating system will help not only in music and audio production but in basic applications in general. Find out what kind of computers are used at the school you're considering, and focus on the finer details, such as audio troubleshooting.
At the heart of every studio is the digital audio workstation, or DAW. For most colleges, Pro Tools will be the main DAW in operation. However, expand by learning at least one more of the big five: Logic, Sonar, Digital Performer and Cubase. For Pro Tools there's a free eight-track version to familiarize yourself with the GUI (general user interface). It's been discontinued officially but may still be available online. If you have a compatible M-Audio sound card, you can download the M-Powered Pro Tools demo version. There are demo versions of the other DAWS as well, but you may have to jump through some hoops to get them.
The mixing board is the hub of the recording studio. Knowledge of how to mix is crucial. A bad mix destroys an otherwise good song, and a good mix can make a mediocre song sound fantastic. Concentrate on grasping signal routing and patching, as you may be called to troubleshoot a studio set-up, a guarantee if it's your own. There are many excellent resources on the topic. Two small but powerful books are "Mixers" and "Mixing Techniques" by Paul White.
Compression. Gating. Limiting. Reverb. EQing. Phasing. Normalizing. This is just a sampling of the processes and effects that are used regularly in audio. Learn and understand how each operates. Hands-on experience is best because it trains the ear to recognize when certain effects or processes are being used.
VST plug-ins are digital emulations of synthesizers, drum machines, other instruments and effects. Instruments are played from a controller via a musical instrument digital interface (MIDI), an audio information protocol that came out in 1983. It has experienced a resurgence in the digital age, and knowing the basic ins and outs, such as cabling, channels, interfacing and mapping helps tremendously. "How MIDI Works" by Peter Lawrence Alexander is an excellent resource to learn about this.