* Learn how to write a Makefile, your builds should be one button/command away
* Learn how to test your code using assert.h, JUnit, whatever, just test all the fucking time.
* Learn GDB, stop using printf to debug.
* Use source control for everything, but especially group work. The groups in your classes emailing code around are doing it wrong, and by the time they'll find out, it will be to late.
* Spend some time in a functional language, and apply what you've learned to your Java/C/C++ class work. Minimizing side effects will minimize errors
Most of all though, get involved with your faculty or department, and try to affect some positive change. The connections you will make with other students and faculty could change your programming career more than anything else you do in school.