I'll tell you what has worked for me. Reading is very important - read everything computer/security/networking/etc related you can get your hands on. When you are in class, ask questions - if your teacher doesn't know the answer, go out and find it yourself. Learn where some of the best security related sites are on the web, sites similar to AO. Read and then play - work at applying what you've learned. The way I taught myself the things that I know are mostly by experimentation and reading - experiment - you may mess it up, but you'll learn how to fix it in the process. Set up a home network like mountainman said, then try to break into it. But be sure to work using your own equipment - never purposely destroy or tamper with equipment not your own. I recently graduated college with an MIS degree - but I've been working with computers since I was about five years old. Now I'm an IT professional, and I'm still learning, reading, and playing. It's a continuing process - that's just the way it is.

As far as programming languages, C/C++ would be an excellent languages to learn but I wouldn't start out with those. This is old nowadays, but I taught myself Qbasic - when it came time to learn Visual Basic, everything seemed to flow right into place. You might look at learning VB, then moving on from there. I wouldn't say that you had to know programming to be good at computer security, but you would need to know the basics and general concepts - of course, knowing a few languages never hurts

Start out with a focus - start with TCP/IP; learn it fairly well, then move on. Don't try to learn it all at once - it's too much

Hope this helps...

BTW - security is an excellent choice for your learning focus.