People are impressed if you can name the current moon phase and tell them what it'll be next. But it only takes a mental model of where the sun, earth, and moon orbits are relative to each other. I also find people are intrigued by the concept of earthshine, and often haven't noticed it until you point it out.
For a waxing moon the circular arc is on the right hand side and for a waning moon the circular arc is on the left hand side [Here in the Northern Hemisphere].
It would have been nice if the mnemonics Decreasing & Cresting worked but they don't. I personally use Developing & Collapsing to refer, respectively, to the waxing and waning moon. Has anyone a better couple of words than these?
In French we have "premier quartier" and "dernier quartier" for "first quarter" and "last quarter" respectively. The mnemonics work with lower case letters: p and d.
In English, the "d" for "decreasing" also works in lowercase, I guess that you can use "p" for "progressing".
And once you internalize this, every image where there are moons pasted into the sky without understanding this will trigger you. It's like bad kerning. Once you see it, you can't unsee it.
