Wait for it.
I don't really have nothing to do at work. The perception is born from the great amount of waiting for other people to do something and get back to you. There are bursts of activity complemented by bursts of waiting. The thing about waiting is you can do it many times over concurrently. So while I only do an amount of work in a day, I can do many times the amount of waiting and do it all simultaneously. Today I completed a significant amount of waiting. I also did work, but relatively little compared to the amount of waiting I achieved at the same time.