D&D, how to create big active groups that run anything but 5E, you got this!
TL;DR: Focus on newbies instead of converting hardcore 5E people, do as much Open Table/Westmarches things as you need, be clear when advertising your game what you do (not) want and cast a wide net in many places online and IRL. Play only what you love.
a. Focus on Newbies and a new group.
Do not try to convert anyone who is used to 5E to anything else beyond one time writing them: "Hey I am 100% stopping 5E. I will be running XYZ from now on, if you are not interested in that, no worries! But if you are really keen, would love to have you play, let me know please."
Newbies do not have pre-conceived notions of how TTRPG or even "D&D" ""should"" be and have not invested dozens of hours in learning and playing 5E nor possibly spent money on books etc. Especially if you pitch it as
"I only run 'Classic D&D', which is way closer to how the 2 creators played it, the books are free or far cheaper, it has some modern rules too and it is way less pages, rules and easier to learn than 5E, I will gladly teach you.", you likely will get people into it!
b. Westmarches. Westmarches. Westmarches/Open (ish) table
The BBEG that wrecks most groups is: planning, setting a date back & forths, life-changes, adulting, people quitting (for a 1000 reasons, game system is just one of many) and cancellations.
A pool of at least 8, but better 12, players prevents or at very least circumvents almost all these problems. It also means that if 1 or 2 people say "Well, I tried non Hasbro rules/system A and G with you but they are not for me, going to quit and find a 5E group instead", you are not starting over from scratch, you can just keep playing.
My groups are not strict Westmarches as I pick the day, almost always a Thursday, always same time and place and the date is always shared in a pinned poll on Telegram (this gives clarity, anyone can see and confirm their date, anytime, with one click).
We generally play every two weeks, but sometimes we skip 1 or 2 Thursdays, if I am away for a vacation, am truly sick or contagious or have something something important I can not do on any other day. Yet, once planned and posted, I almost never, ever cancel sessions.
I think cancelling, without a very good reason, is a messed up thing to do. So much so I wrote about it:
https://anon0.bearblog.dev/dd-dnd-how-it-truly-matters-to-adults-why-i-dont-cancel/
All the things that I do in terms of logistics and communication very much help to avoid any confusion and pre-clude so many messages and borderline bartering over who can (not) make which day. Either you keep at least some of your Thursday evenings free every month and you vote "I can make it!" in polls, or you do not play. Easy, clear, fair.
However players do organize among themselves in terms of which five actually play next time, in the cases when more than five people vote "I can make it!" we have a simple solution. In that event, one or more people might sit out the upcoming session but they will get preference the next session they sign up for. The players always send me a list of the final five who will show for the upcoming game.
As for what kind off of person turns up, even for their very first session with me, I always know. I have a pretty extensive selection process for who I add to the Telegram group/our pool in the first place. My process involves every prospective new player having to first read a 10.000 word shared document with the group's preferences, style of play, tips, few game rules and what they can expect. This text also includes many reassurances and simple, obvious but still important to state things like: "modulate your voice to the softest spoken person at table, do not interrupt, let everyone decide and shine." For newbies especially, this is invaluable.
It works exceedingly well for us. Yet I am not suggesting anybody else has to go as far as our group or write anything near 10.000 words! Just a few lines instead, in which you tell new players how you (don't) want to play, certainly never hurt any group. Much has been written about "session 0" as well. Doing either of those or both, can ensure you don't end up with easily avoidable problem players or annoyances, for other players as well as the DM. Which is better for everyone in the group and the group's future viability.
We do usually end the session in a safe place or will at least have finished a section or "dungeon" (in the broadest sense of that concept). Our style may not work for everyone, but we all love it and every one knows it coming in. If any DM manages have the exact same 5 adult players at the table playing weekly or twice a month for even 10 sessions in row, without stress, issues or a ton of planning, messages and few cancellations,.. never mind manages all that for 25+ sessions, kudos! :)
Myself, I tried "same 5 people every week, or two" for decades and with so many groups and people and it was an exercise in frustration, logistics, planning nightmares, cancelled or delayed sessions, disappointments, and ultimately, ruined a lot of the fun for everyone, me most of all. It ended a few groups. If I as host and DM am having a bad time, that reflects on entire group and all players too. The groups I have been running in the way I detail in this post have been going strong, and happily, for many years now. They show 0 signs of slowing down, quite the opposite.
I am never going back to same 5 people every week, or at least not until my players and I have retired. 5E and very similar, Hasbro owned D&D,.. never will play those again, pointless and almost abhorrent to me personally/my taste.
I very much don't like the mechanics, the rules, the cost, the long and quite complicated books of that version of D&D, nor do I like the complete lack of ethics of the company who sells them. There was a time (I was not even aware of the existence of the OSR then) that all that wasn't the case for me, or at least not to that degree. Hasbro D&D was all I knew and at the time, and was certainly worth playing, so I am absolutely not faulting anyone who is playing it.
If you and your entire group are having a great time, you are doing it right.
I do just hope all people try a few different TTRPGs some day. Having choice and options is never a bad thing. I had a pretty good time back then, I now have an excellent time! Switching systems has vastly improved my work-load and enjoyment as a DM, which means my entire group has benefited and all our sessions have gotten a lot better.
c. The recruitment never, ever ends
I have a few posts on Reddit with very clear info about how and what we play (and just as importantly what we do not play) on the subreddit of the city where I live. I repost my pitch every 6 months, at least. Because I found out in practice that many people who will actually gladly join your group,.. do not use the search function, or assume that an old post no longer has relevance or no more players are needed.
Reddit has worked out amazingly well for me for making IRL connections, not just for D&D. But there are many avenues besides it, from a flyer at a board game store to any social media or messaging apps, or asking people at work, and so much more. All those can be great ways to find players. Most of my players end up with me for years, but you never know, life happens! Plan for that. Have a pool of players, add people as necessary and as it comes up, especially if new people you find seem like they may well be an excellent fit.
d. How doing all this worked out in practice:
Been doing most of it for 10 years or more I think. I have never played online and don't really plan to, it is awesome that it is out there, but I truly want less screen time, not more, I already work online and am online plenty in my spare time as well.
In Berlin (big city) I ended up playing with 40 ish people total (at least once) of those, 15 or so became a hardcore primarily Westmarches group that plays often, including today, as I write this. Sometimes they have 2 sessions a week. This group spawned 3 or more DMs and campaigns and added another ca. 6 players after I moved away from Berlin. When I am in town, we still play sometimes! A few of those people became very friendly acquaintances and I do other nice stuff with them -besides D&D- when I am back in my old haunt.
Currently, in Valencia, not a truly big city (800k people) I have a group that had a total of about 25 persons over 3 years, which played with me at least once. Of those 25, 11 remain and also 2 are DMs with their own campaigns or one-shots and we all play with regularity.
Always with 5 players and the DM, but having about 11 active players in the Westmarches pool means that even with: vacation, holidays, illness, adulting, jobs, kids etc sessions are never cancelled due to lack of players. In both groups above more than half of players were newbies when they joined, but we also have a few persons that have been playing since late 70s or early 80s, of course they get Old School play. :)
What if I don't live in or near a city?
Some people will say "I live in a small place, with a low total population, I got no chance!"
Not true, I know people who have done similar in small or even rural places. The good thing about smaller, low population communities is that your TTRPG game is not competing with dozens of other TTRPG-groups, nor a plethora of other leisure activities happening all the time. Worst case scenario, there is always online play.
But you might just find that some people in small places truly value having a frequent social and fun face-to-face get together and will consistently have or make time for it! Sure, you might need to ask around at (volunteer) work, and put fliers at the community center or a club and maybe a farmer's market and certainly the library.
You may have to go to area-specific groups online and post, or drive -an hour even- to pin a tear-away flier at the nearest Game shop, etc. But if you have not tried at least 5 avenues to recruit players, you can not possibly know how many potential players there are in even your small neck of the woods.
We have played: Basic Fantasy RPG, MOTHERSHIP, Pirate Börg, Mork Börg, Knave and few more. For some years now we have primarily settled on Shadowdark, since then especially, all the players would not play 5E no matter what. They know too much and they love non-Hasbro stuff too much. It took a bit of time, especially for those that had played some 5E in past, but all of them came around and vastly prefer OSR games now.
For us, Shadowdark has a few of the best things of 5E and almost none of the bad things. All the players will gladly try or run lots of other OSR, NUSR and homebrew systems and things. We are not stuck, on any one system or setting.
I am not saying all the above is easy or doesn't take time, but it is very doable and extremely rewarding. You will find yourself having a blast and, in time, perhaps even making 1 or 2 great friends.
The sooner you start and the more clear you are about what you do -and do not- want, the more likely that you will in a few weeks or months from today, having the best time playing and running exactly what makes you happy, with like-minded people.
All that makes it far more likely you will avoid: DM burnout or even quitting wholesale for months or possibly years. Before I knew and did the above, I quit for a number of years due to system (way too many rules and too much prep with Hasbro stuff) planning and recruitment issues. In hindsight, there were certainly solutions. I was just not aware of them. I wrote this post so others do have that information readily available.
To quote my favorite Dungeontuber, "Dungeoncraft/Professor DungeonMaster":
"Life is too short my Friends, to not do what you want to do, you will regret the games you don't play."
https://youtu.be/G09eeu8Y3SY?t=556