What are Google's rules for RSOC?
In summary: the page must have real standalone value and not be mostly ads; publisher-suggested terms must be relevant; visitors must not be encouraged or misled into clicking; any advert used to buy traffic must describe the page accurately; and the full advert text must be passed in referrerAdCreative. The feature must be enabled and the design approved by Google.
The RSOC policies sit on top of the general AFS program policies and Google's publisher policies. Related search is a "product-integrated feature" of AdSense for Search, with common rules on placement and deceptive implementation, and specific rules on partner-provided terms and traffic acquisition.
A few points catch people out. The unit may not go on pages with insufficient content or too many ads relative to content. Content pages bought with traffic should use "learn more" style promises. Terms sent through the terms parameter are filtered by Google. And compliance is ongoing: publishers that fall out of good standing lose features. Read the current Google help pages directly, since wording changes and a provider's summary may lag behind.