"We're better than those nine other guys on the page. Click here to find out why."
I will tell you an anecdote about our Yellow Pages ad. When we were starting out, we had Yellow Pages ads. We got some discounts from the phone company, and as we were doing local web site hosting and development, we actually got leads from the phone book occasionally. But there were a ton of other web development and hosting companies listed. And our company name began with "M" so we didn't even have an alphabetical advantage. Hard to stand out.
One of the things we heard over and over from clients who did make it down to our listing was that they'd called a bunch of the other companies first, but either got voice mail, or nobody picked up, or were left on hold. By the time they got to us, they were actually pretty pissed with the whole process.
So when it came time to redesign the ad, and we had a little extra space, I told them to add "We Answer the Phone!" in big bold letters.
You would not believe how much of a difference that made. Something not even web related, or specific to our services. Jsut the fact that a human being would pick up the phone when you call. We always ask why people first choose us, and they'd tell us it was because we said we'd answer the phone. And we did.
Ten years ago our three largest clients came to us specifically because said we answered the phone - and all three are still with me today. They make up 90% of my client work.
Nowadays, it's not Yellow Page ads, but it's meta descriptions. Same thing applies. Find a weak spot in your competitors, and drive a truck through it.