I've written in recent weeks about how to handle a Reading Comprehension passage when time is running out, and in thinking about that idea--Reading Comp pacing--I feel it's important to briefly address one of the most common elements that students find slows them down: diagramming.
Here's the thing. Any time you find yourself stopping to make notations, be it for a passage, game, or LR stimulus, you're using valuable time that could theoretically be spent doing something else: maybe continuing to read the passage or stimulus, maybe analyzing answer choices and considering which is correct, maybe just getting to those final few questions you would have otherwise had to guess on. What that means then is that the time spent writing needs to be an investment, where it either gains you more time than it took as you continue on (like a prephrase, where you can more aggressively/efficiently sort through the answers), or it translates into an improved understanding of what you're facing such that you've increased the likelihood of getting the question correct. Failing both of those, your diagramming was probably a poor investment and you would have been better off without it.
Consider an all-too-common scenario: Student X begins working through a Reading Comprehension section, diagramming fairly heavily as she goes--writing brief paragraph summaries in the margins, bracketing, numbering, underlining, and all the rest--so that on average it takes her 4.5 minutes from beginning a passage until the end of it. Another 5 minutes for the questions, and she's right at the 30 minute mark as she moves to the fourth passage. That leaves 5 minutes for an entire passage and its questions, which is a tall order for even the best test takers (again, I wrote about what to do in this situation in a previous post).
Now consider that she could have been just as successful, or at least very nearly as successful, without the vast majority of those notations. Imagine that instead of writing out paragraph summaries, she simply paused very briefly and considered the main ideas of each paragraph in her mind, writing nothing. Perhaps instead of furiously underlining she just made mental notes of key information or critical points, recognizing where they appear and their significance, but not annotating it in the text. How much time might that save? 60 seconds per passage? 90? Even saving just a minute per passage means that she'd have over 8 minutes to finish passage 4, instead of the mere 5 minutes remaining after heavy notating. And if you've ever spent any time with Reading Comp on the LSAT you know what a difference those extra 3-4 minutes can make!
I'm NOT encouraging you to never diagram! In fact, it's a necessity in Games, and probably critical for certain passage elements and LR questions, as well. Rather, I'm encouraging you to consider how much time you've spent making notations, and whether that time was well spent, or could have been better spent elsewhere. My experience tells me that if you're like the vast majority of test takers the amount of time you spend making notes is, in actuality, a pretty poor investment and costing you way more than you gain. With that in mind here are a few tips on how to make any notations that you do choose to show less time consuming and still powerful enough to convey the intended point.
For Reading Comprehension:
A lot of people feel the need to write brief summaries for each paragraph or at the end of the passage. STOP. Feel free to pause occasionally as you read to collect your thoughts, but odds are you won't need to write them down.
It's usually better, both in terms of clarity and speed, to notate outside of the passage text than within it. For instance, brackets beside text are both faster to create and less prone to obscure the words than underlining or circling in the passage itself.
Once you finish reading a passage and making any notations, and after you have answered the questions and analyzed your performance, reconsider what you chose to diagram and think about its utility. That is, how long did it take (approximately), and to what extent did it improve your understanding of the passage and your ability to answer the questions. The point of these considerations is to determine what notations you could have done without, and how much time that would have likely saved you; on future passages then you'll have a better sense of what/when to diagram to maximize its value.
For Logical Reasoning:
As with Reading Comprehension, most LR diagramming is likely to prove unnecessary. Ask yourself questions like, "did I really need to underline or mark the last sentence as the conclusion, or was simply recognizing that the last sentence was the conclusion sufficient?" The key is notating only what you need in order to obtain the greatest degree of speed and insight.
Certain stimuli do tend to be well-suited for diagrams, however: questions with Formal Logic, questions with conditional reasoning chains (A --> B, B --> C, etc.), and even occasionally questions with causality where you can quickly sketch the cause and effect...diagramming in these instances often is worthwhile for a lot of test takers.
For Logic Games:
A main diagram, as well as individual diagrams for certain questions, is required for every Game. The only "exception" to this idea isn't really an exception as much as an adjusted application of it: some Games won't provide much information to help you create a main setup--certain Pattern Games, for instance--and you'll simply sketch shorthand versions of the rules. Even here though you'll still want to notate the variable sets and restrictions given.
That said, you should still practice to represent variable sets, your base/structure, rules, and inferences as efficiently as possible. Go back after completing a Game and consider your setup: which elements within it could have been represented more quickly or effectively and still been clearly understood?
Hopefully you can see that diagramming on the LSAT isn't something to steer clear of, but rather it's a process that should be refined through continued trial and error, and lots and lots of practice. Your goal is always to find that perfect nexus where ultimate efficiency meets complete accuracy; diagramming will certainly play a role in that synthesis, and it is your job to determine exactly how to best incorporate it for your needs.