It takes some mental work to put a chart on a page in a readable form. I found that my one page landscape approach helped me immensely by giving my a template to work with. I could use a ready-made 20 entry table and focus more on the contents. Often the constraints of the form were generative; I had to push to get to twenty entries or revise my categories to what I saw as most essential.
You can see the pattern on my DM aids page. It's basically a single letter-sized page with 20 items in a table and enough room above the table for rules governing whatever system I was looking at-- magic rings, potions, diseases. With the drugs table I offered up only 10 effects and space below to mix and match them as you please. I liked that even more and I think that kind of approach-- a selection of fundamental options and space for you to make your own combination of them-- is probably the best way you can do these kind of rpg charts.
I have knots, fireworks, and potentially martial arts waiting on the back burner to be put into these one-page formats. But on to layout.
I've mentioned before that I think an A5 sized book with coil binding might be the perfect size for an rpg book used at the table, during play. Books meant for prep work can be more free in their dimensions, heck it would probably work better to have oversized books for preparing your adventures. You could fit 100 entry charts on one page in easy to read type, diagrams, etc.
I'm more interested with a reference to use at the table right now. What I'm currently using is a plastic report folder with plastic sleeves that you can slip letter-sized paper into. I have it full of my one-pagers. I would like something more elegant and efficient.
I went poking around on lulu and was surprised that not only do they offer A5 as a printing option but you can have it coil bound and download a template to help you make it. So I downloaded the template. It has large margins and gutters. And you can probably guess where I'm going with this.
I have no idea how to fit my one pagers in that format. I thought at first to rotate my tables back to portrait and try and span them across two A5 pages. But they just don't fit. I can't fit twenty entries on that size page, much less the subsytem instructions.
The cool thing about two letter sized pages is that I can have the one-page rings on the left page and the The Ring is Actually page, with options to spice up the basic list on the other. The two page spread lays out everything I need to know about rings in front of me at once. I don't think that's possible with A5. Just not enough room.
But that's the point in wanting A5, right? That you don't have two letter-sized pages to try and spread out across your map, miniatures, and snacks. I guess it comes down to what I will need in prep and what I will need in play.
While that seems a pretty straight forward question, I think my one-pagers were an attempt to make things that are normally considered prep-work, efficient and organized enough to help me be confident in off-the-cuff play. So rather than flipping through a huge DMG to find the treasure section, I could say, "okay, this treasure has some potions, a ring, and some drugs," and quickly flip to those pages and get it done. In that sense, being ready for whatever players might do, most of what could be considered prep-work infrastructure could also be handy in an easy-to-use-at-the-table format.
Well, my one-pagers are also helping me learn the game. By forcing myself to rewrite these subsystems, I have an intimate understanding of them and can shape them in a way that makes the most sense to me. I suppose the best thing for any DM would be to go through this whole process themselves. But I like to think if we share these kinds of things we can build on top of them and spend our energies making other cool things. And also, if you have a system laid out in a clean and organized way it should be easier for you to see what you want and what changes you might make.
So, I still need to think more about what information and in what format would be most useful for me at the table. And I need to play around with the A5 two page spread to see what is possible.
If you feel ambitious, I'd love to see how you might put the info from one of my one-pagers into a two-page A5 spread.