Be amazing in your schoolwork, regardless of what it is you do. Always do more than you're asked for. Beat out the competition. Blow them away with your work. Come up with fantastic concepts and ideas - something you know others wouldn't think of. Always go for something that would make people think "dang, now that's clever!" These are the teachings of my former Advertising professor, Douglas Davis.
In his class, I learned how to truly work as a team with partners, how be actively productive, and how to go above and beyond what I thought I was capable of. These are the types of professors that shape and mold us into who we are as professionals.
When you're just entering the working world, you don't have much experience under your belt. Your schoolwork is pretty much the only thing you have to show for yourself. For designers, this means that your portfolio does most of the talking. For those with careers that don't involve portfolios, your resume should list your accomplishments, activities, and so forth that define who you are and what you're capable of.
By mid-May, I will be launching a portfolio that will highlight a lot of my schoolwork. It will including some great advertising campaigns I worked on in Douglas Davis' class. I can't wait until it's up an running!