I've been thinking a lot about how writing resembles picking pockets.
I used to make my writing classes watch this video of famous pickpocket Apollo Robbins explaining how he directs his victim's attention to where he wants it (and away from where he doesn't want it, like your wallet).
Turns out that attention is almost like a liquid: it can only be in one place at a time, and it can be directed. The principles behind Robbins' abilities are the same as the principles of good writing and editing (although obviously the methods of directing that attention flow differ).
Readerly attention can be gated (stopped completely), choked (the attention channel is narrowed, slowing the flow of comprehension), and pushed (the floodgates are opened wide and the attention tumbles ahead breathlessly).
Generally, when readerly attention is gated, it's by mistake. These are often errors that bring your reader to a halt, forcing them to read and re-read a sentence in order to make sense of it. For especially sensitive readers, even a misspelling or a grammatical error stop attention from moving forward. This is rarely a good thing; each stop causes the reader to doubt the author's credibility a little more, and at some point most readers will simply walk away.
Choking the reader's attention can be done deliberately or accidentally. When deliberately done, it's a useful element of pacing in both fictional and nonfictional narratives. (See, for example, Eric Hayot's work on the shape of paragraphs and sections, and the peaks and valleys of attention created by those shapes, in humanities writing.) When it's done by accident, you risk slowing the reader down in spots where she should forge ahead. Several things can cause this. Multiple shifts of sentences' grammatical subjects within a single paragraph slow down your reader; besides violating one of my most cherished of Joseph Williams' style principles, this forces the reader to do the work of figuring out how these seemingly disconnected sentences link up. (This is so, so common in literature reviews.) Another slowing device is using very long sentence and clause units, which are difficult to parse. Generally, the longer and more complex the syntactical unit, and the more complicated its relation to other parts of the sentence, the more slowly the reader moves through it.
Pushing the reader's attention forward can also be accomplished in many ways—punctuation affects it (breathless-sounding sentences, separated by few full stops and employing lots of connecting devices like dashes and commas, pull the reader's attention along with them), and these are usually intentionally used by authors. Sometimes short sentences do it. You can also keep the reader's attention speeding along the surface of the stuff you want them to pay attention to by "shadowing" any information that you do not want spotlighted. Anything in subordinated parts of the sentence—which clauses, parentheticals, etc.—is treated as less weighty. By putting less-important information in grammatically subordinated elements of the sentence, you can help the reader know what to pay attention to and what they can safely skim.
These techniques are difficult to articulate, but I think this is one of my greatest strengths as an editor. I can intuit what ideas or elements are crucial to your piece (thank you, decade of graduate school in literary studies, for making me a freakishly sensitive reader) and then shape the prose's pace to shadow the details and highlight the central bits. I love helping authors de-emphasize the things that don't matter and focus the reader's attention on the essential elements.