Credibility is crucial in this business. And one way to build credibility is by becoming an "expert."
How do I define an "expert?" One who has mastered something enough to teach it to others... and then does!
So, this technique is simple:
Don't think you don't have anything to write about, because you do! Do you understand tracking? I just saw an article in an ezine about tracking! Do you know the most powerful word in an ad (it's "you")? I just saw an article about that on AOL.
Brainstorm. The things that are obvious to you are things that others still need to learn. Look at the articles that you're getting and wonder what variation on those you could write from your research and/or experience.