If you are answering an ad, make sure you read it in it's entirety. You may see that something they are looking for applies directly to your skill set and you can use it to your advantage when writing your cover letter. I was looking for a job as a television production assistant. I read an ad from a shopping network looking for production assistants. In addition to the usual and customary requirements -- like "someone who gets along with other people," "a self-starter," "someone motivated" -- I noticed they were looking for someone with nice hands for possible hand modeling. In my first paragraph, after mentioning my education and experience, I wrote, "And did I mention my beautiful olive-skinned silky-smooth hands?" I know this small attention to detail on their job description really made me stand out. I got a call to come in for an interview and was hired on the spot.