Sample partial feed: Ars Technica <http://feeds.arstechnica.com/arstechnica/index/>
Provide sufficient content to give for readers who will have to decide whether to click through to your site to read the full story (at least 2 to 4 paragraphs of text)
Showing the number of remaining paragraphs is also a good indication for readers.
Good visuals that support your stormy make for a nicer reading experience in feedly, including for partial feeds.
Be sure to use high resolution images
Have a website that is optimized for mobile