The words you use.
Writing a job ad is all about the words you use. Literally and otherwise. With a job ad you only have a few moments to make an impression.
So what do you start with? How do you sum up a job to make the right potential applicant apply and inquire? I believe its as easy as thinking about what you perceive as interesting and important enough to read. Think about what would make you interested in the job ad. If dry, boring words wouldn't attract you, why would you start your ad that way?
This doesn't mean to forget your audience. Making your ad interesting is a big part of keeping potential applicants reading, but when you're talking to a specific industry - you still have to be the expert. Your introductory words have to be intelligent, witty, and intriguing.
Think about what it takes to make a connection with your potential applicants. Think about what it would take to make a connection to you. Its easy to assume someone is going to read your entire ad, but without a compelling hook and intro you wont have anyone to read your ad.
Being a good recruiter and staffer is all about making a connection.