Oh boy, I actually have first hand experience with this.
The Montreal scene was non existant almost directly after the release of MK9. The summer after evo it died here, and it was just Zaf and I, and I was barely playing. I went to NEC in December and that got me back into the game, so I thought I wanna start up a scene.
I started posting in the Montreal Thread, saying we were going to host causals at a local internet cafe(for fighting games pretty much). That's where we met
LolingOctopus (Who actually is one of the main people in our scene right now) and he brought along a couple of his friends. Each week on Sunday we would host these casuals and a couple more people would come, so I started to do Ranbats (with money involved) to keep people interested. This went on for a couple months with quite some success, we even had streams if some people here watched which I think went pretty well.
It then died out again, people stopped showing up, but now there's an uprising of people again, I'm trying to host as much as possible.
The main thing is to keep people interested, and always give as much feedback on their gameplay as possible. There's so much potential with people, but they just need to be told what to do. Some even are too scared to ask for some reason for criticism or for casuals.
You need to know your scene, get to know everyone and help them improve, always run events to keep interest.
I usually run the MK tournaments when there's a major here (With help of the SF scene), and we had 20 man tournament a couple months ago (which isn't bad for this scene). Things are picking up again and I think Montreal is leveling up as a whole moreso now, rather than a couple players just leveling up.