We're working on a side site for a project, which is based on WordPress. The site has posts, pages, photos and videos, most of this content is of informational nature. However, the site's intention is to SELL, thus it has CTAs (call to action) and a few products (think DesignModo or Envato only that with less than 5 products of much higher value). The information in this site is AMAZING, so it's not secondary at all, it has been carefully crafted in order to create a big and loyal audience
So it were just a marketing site, I'd use the footer as a "last chance", which is what we usually do for this kind of sites. For a WP informational site we'd use maybe a posts and pages list, maybe a small contact form.
But so far, I have seen it all: mega footers with lots of posts, twitter feeds, forms, CTAs, instagram posts, copyright, design notes, sitemaps, minimalistic footers, header replication... anything and everything, I've seen a lot of footer versions, but wondering: is there a set of recommended elements that I NEED to have? Specially in the context of a site like I'm describing, but general answers accepted as well.
Studies and research would be enormously appreciated!