If you are making RPG products and want my two cents, read on for the changes I'd like to see:
- The standard stuff we all know. Tighter formatting, focus on visual design rather than walls of text, less bloat, usability-at-the-table, etc. Art is fantastic to include but it should never, ever disrupt the usability of the product.
- Don't put character creation before rules explanations. This is almost universal, with the rationale being, "we want players to be able to jump in and make their characters right off the bat!" But most of what's written in character creation won't make sense to someone who doesn't know the rules yet, so you can't actually make your character yet. At least, not in an informed way. Not only that, but I want to know what sort of game this is before anything else. How does it play different from other games? What are the universal truths of this game that won't change no matter who you play?
- Character creation should probably focus specifically on the character sheet itself. Some games do this right, and it's great. In fact, some games (like Mothership) merge the two completely: the character sheet is itself a flowchart to make your character. But even if you don't go that far, I do still insist that you begin the chapter on character creation with an embedded image of the character sheet, fully labeled and accompanied by the numbered steps on how it ought to be filled out.
- Try try try to always have a sample adventure to play if you are releasing a new system. I know this is a whole 'nother extra thing to do and you just want to put your game out there. But for most games it's extremely necessary. I don't know about you, but I can pick up a new system, read through it, and get a handle on it pretty quickly. But designing adventures, and I mean good adventures, is one of the more laborious tasks for me as a DM. If you have a simple, universal game that's meant to be compatible with most things, then maybe you can get away with skipping this. But if you have a game that has a whole new thing going on, like thief/heist mechanics or players piloting mechas or using some kind of new and innovative mystery investigation mechanic or you have rules for fighting giant creatures a la Shadow of the Colossus or something like that... we need an example to see how it should be applied. More than just a "sample of play" transcript. A few months ago, my group played two sessions of the wonderful 1-page RPG Crash Pandas and it was a blast. But the GM had to design about half the "game" just to figure out how to write an adventure that uses these rules.
- In adventure modules, open with a roster of major characters (sometimes it's titled "Dramatis Personae" and I like that) and something like an outline of events, network diagram of factions/NPCs and their relationships, and other stuff that helps the DM get a handle on the whole thing up front.
- Also with adventure modules, don't be afraid to provide handouts rather than trying to make it work as a contained book. An image that's only printed on a page of the book is an image I probably can't show to my players easily. Even worse for a map. Seriously, don't be afraid to print a map for me to use. I'm so sick of adventures that heavily rely on the use of a provided map but then only print the map in the corner of a page filled with spoilers and for which the room descriptions will continue on for another 6 pages that I have to flip back and forth between. Monster statblocks? Put them in a separate booklet like the original Dark Sun boxed set. Got a timeline of events I should be tracking? I would like to have that as its own sheet on my side table so I can regularly turn to it, mark off an hour, check what the next event is, and return to the rest of my DMing setup in front of me without having to move anything around.
- Magic systems and other things that require big indexes are often a pain to consult because of organization. Most systems just have them sorted alphabetically, but if you can think of a better way that makes more sense for your system, then try that. For example, spells sorted by level is usually better. If you have a list of perks/feats/techniques/whatever, consider finding a way to categorize them intuitively. If they have prerequisites and form "skill trees", then group together the related items (even if their names don't alphabetically follow from each other).
- At this point, most people are learning to include fancy things like bookmark ribbons and inside-cover reference tables and whatnot. But here's something I still don't see as commonly as I should: if it's a thick book and you have the production value for it, use a colorful edge index on the side of the book's pages so I can flip around easier. I use those a lot.
- At this point, I think there should always be an accompanying digital version available. Big publishers like WotC will have a code in the physical book for you to retrieve a digital copy, which needn't be purchased separately because it's just a part of what you've paid for already. If you are selling online, always have a PDF version available and make that shit optimized with hyperlinks, bookmarks, and printability (because there will be pages that the consumer will want printed off even if they didn't buy the physical book).
- Any game I play long enough (Pathfinder 1E and then D&D 5E being the main ones), I always eventually download fan-made custom character sheets tailored to each class. Well-made ones are amazing. I'm not saying that you need to have those in your book, but if you have a relatively complicated and character-creation-focused game then maybe consider having official "class-specific character sheets" available for download somewhere instead of relying on fans to do it.
Thank you for reading my kvetching.