Ask HN: How do you handle direct ad sales?

I recently discovered that, on some properties, the money that can be made from direct advertising relationships far exceeds that of AdSense. So, do you have experience with this, and any advice?

Specific questions: please answer one, all, or just offer advice. Thanks so much.

* How do you craft your agreements? Is there a specific contract you like to use, or do you just keep it informal?

* What level of reporting do you offer to your advertisers?

* How do you handle raising rates on advertisers?

* How do you bill? Do you just manually send invoices, or is there a tool that you use?

* Any other good-to-know's?

[UPDATE] One more question: any good marketplaces for finding advertisers?