I've always enjoyed teaching. Back in 2010, ink still practically wet on my CPA license, I took a huge swing. I pitched a workshop to my absolute dream event: Sock Summit, a giant, short-lived conference for sock knitters. When "Accounting for the Wooly-Minded" was accepted, I promptly overthought myself into a panic. So I did what I always did when I noticed I felt overwhelmed in my 20s: I asked people for advice.¹ My dad passed on this gem he'd gotten: pick three (exactly! three!) takeaways you want your students to leave with for each contact session. Build the rest of your lecture/workshop/lesson plan around the conceptual scaffolding and repetition needed to get those three (and only three) things into their brains.

I've used this advice nonstop ever since. It works for 1:1 knowledge transfer and coaching, as well as for group lectures and workshops. It helps me chill out² when preparing, and learners seem to like it. With grad school prompting me to think endlessly about instructional design, I've been pondering why this advice works. I think there are three³ main reasons:

1. Cognitive capacity is limited. While research on working memory continues to evolve, hanging on to three concepts is doable for most adults most of the time. I like to think of the learner as a person on a trip with mostly full luggage. They just don't have room for that many souvenirs, no matter how interested they are or how good a teacher I am.

2. Any three points can form a plane, geometrically speaking. Imagine your learner as a person attempting to balance on a board supported by your concepts. Choosing three concepts with reasonable care means they have a shot at achieving a stable surface on that board without needing to find something to shore up a wobbly bit.

3. A framework for editing/prioritizing/curating your plan is almost always a gift. Consider the blank page vs. a fill-in-the-blanks Mad Libs-style worksheet. Which of those is easier to start? I always, always want to teach way more than I have time for. I have more relevant funny stories and fun facts than will fit. Following the rule of three forces me to prioritize and notice which topics are actually parts of scaffolding, not concepts ready to be load-bearing on their own.

I've also taken to using this advice in reverse: in any class, workshop, or reading, when I get to three useful concepts or "ah-ha" moments, I shift gears. I stop walking the beach looking for cool rocks to put in my pockets; my pockets only hold three. I leave if that's viable; if not, I start letting the content wash over me. If there's another cool rock, I maybe take a metaphorical picture of it or jot a little description of it, but I don't try to carry it out with me⁴.

And since I've now told you two ways to apply this advice, I'm thematically obligated to offer you a third. When the reading is boring, or the workshop is not to my taste, but I have to stay put, I collect three ways I'd make it better if I was asked. Three is enough to vent my frustration, and sometimes after venting, I find something I'd like to carry out after all.