A reader wonders:
Some of the networks I am interested don’t belong to Google’s Content Network (specifically craigslist.org and kijiji.ca). Will I have to make another campaign only for these 2 sites, choosing the option in the content network, "Relevant pages only on the placements I target" instead of "Relevant pages across the entire network."
If the sites aren’t in Google’s Content Network, then you can’t specify them. They don’t give Google permission to place ads on them.
If you want to place advertisements on a non-AdSense site, then you have to contact the site directly or find the ad serving network they use.