All of the advertisers on my own site are gained through the "Advertise with us" link, as well as recommendations to others from previous advertisers. I do it all myself, and I rarely have unsold ad space. I have had quite a few large companies place ads with me as well, but I have never solicted them myself.
Judging from my keyword referrals, there are many people searching for sites to place ads in my market. So never underestimate the value of an "advertise with us" page.
When I see an advertising page as a potential advertiser, I want to see a few key things:
1. Availability dates - can my ad be placed within the next week, or are the ads booked weeks or months in advance. And I want to know that this site is current and active.
2. Detailed advertising options spelled out - I want to know how much the ad spot is that i am considering. Autoresponder information is fine, but "email us for information" is a pain.
3. When should I expect a response, and when should my ad appear online?
4. No PDF rate cards - they are such a pain for me, LOL
As an advertiser, I was considering placing a very pricey ad on a large site - I didn't even get an email response to my inquiry for a little over 4 months. With that kind of response time, there was no way I would pay to advertise there with such lax customer service.