If you want to do the startup thing, notice people who are smart and more ambitious than you and spend your time hanging around with them.

If you want to have your pick of a quality corporate job and find your excitement elsewhere, build something tangible you can point to during an interview. It doesn't have to be complicated, it just has to indicate that you can accomplish something on your own.

Remember that becoming an expert in anything takes 10 years, so assuming you are around 20, think about what you would like to be an expert at when you are 30 and start working on it regularly.

Edit: One more thing -- college can be one of the last times in your life when it is trivial to make new friends. Make as many as you can, and try to hang onto the good ones after you graduate.