Keep an eye out for large, ordered collections of bite-sized chunks of similar (but not too similar) intellectual material. This is the kind of thing that I like to use for exercises, like a paper with many proposed engineering techniques, a site with many social science results, the many answers to Edge.org questions, or news and commentary pieces from a journal’s website. These can be used as a large yet sufficiently sophisticated supply of fresh examples to practice on, kind of like how I used a hymnal to get better at sight reading back when I had a tendency to memorize everything I played. In a similar sense in Thinking on the page, I mention film review collections and textbook physics problems in the almost the same breath. Or, more generally, these can be useful not as literal exercises but as something where you might learn more from many small instances than from one large account; this is one reason I like the histories in Beyond Discovery. Notice such collections in the spirit of effectuation, not optimization: rather than work backward from the thing you want to practice, cultivate awareness of the affordances of material around you.
Extra credit: Devise an exercise using a source you find.