Nice to see the thread hasn't imploded yet.

On the topic of RPs n all, from my point of view, there's two ways in which players are drawn/stuck with a RP: the promise of a fun plot, and the potential for characters to grow. If you can formulate an idea that offers both ways, that's even better! To clarify what I mean, I guess I'll ram in some examples...

[hider=Sorta long ramble, after retrospect]
School-based RPs are essentially all about character development. If this is a battle school, people can look forward to growth in terms of their supernatural or martial abilities. If this is a SoL school, people can look forward to hooking up and causing melodrama. If you add in a concrete overworld plot ("This is a post-apocalyptic world with a dystopian government who sends superpowered teens on ridiculously lethal missions"), you heighten the potential for even more positive/negative developments by letting your plot spark inter-PC drama. Sometimes, it backfires by making people get pissed OOCly at each other, but I've seen at least one time where it worked VERY well, and culminated into a RP that didn't lose any players at all. Initially, it's the promise that something special will happen to your character, and your character alone, that draws in interest, whether it be GM-sanctioned power upgrades or a trashy, dumpster-fire romance sparked by an encounter gone horribly wrong.

As extra examples, Ariamis's Magical Girl CYOA makes character creation hella involved by adding in an element of randomness that gives people ideas about their character that they wouldn't immediately have thought about or considered on their own. Rune's Epic of Beginnings encourages making cool, heavy backstories (cult leader, literally Oda Nobunaga) because you get a superpower based off that backstory, and then afterwards, that backstory can be used to inform your character's trajectory through what is otherwise a sandbox-y setting.

Adventure RPs depend on having a delicious plot to draw people in, and they paint a fantasy of involvement, of being part of something that'd change the world rather than yourself. Sparking a rebellion, escaping a prison island, killing a dragon, all those pull in attention through having any character you make involved in something lasting, something big. If you can get people excited about what they're going to do, and what they're going to plan against, then that excitement can be the momentum you use to drive the RP until they've become invested enough that it'd feel bad to leave. Conveying the idea that they'd have something to do immediately when IC begins, and then carrying through with that promise, gives potential players something to look forward to, and then something to enjoy. In this case, even people who're not interested in having long, philosophical chatter with other players can enjoy the RP, just by beating up baddies or braining themselves outta dicey situations.

As extra examples, Valor's FEARLESS had a hell of a start where PCs of a rebellion immediately crashed a prison to get someone else out, had a deadly encounter with an elite guard of a dystopian, superpowered government, and managed to escape after suffering a good amount of injuries, and all [i]that[/i] really materialized the sensation of how shit is definitely real, how kid gloves don't exist at all. RC3's Goblin Quest offered a sense of achievement just through the mundane-est of things, such as beating up and eating raw rabbits or crafting random tools on your way to surviving, which worked out well, cause the players start as orphan goblins trying to figure out how to get strong fast, before the humans that slaughtered most of their tribe find them.

And if you can mix plot and development together (Yankee's Windfall comes to mind for creating an ensemble adventure RP where everyone's traveling together around the continent to fulfill different quests that have personal/continental impacts BUT THE SPECIFICS OF HOW THE PLOTS WILL GO IS PLOTTED BY EVERY PLAYER EXCEPT FOR THE ONE WHO PURSUES THAT PLOT), then it becomes fuckin' delicious.
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If you can convey the sense that such things are possible, AND the sense that you're able to offer that to players (which may really just be something dependent on something as intangible as the vibes that your post gives off), I think that there's a pretty good chance you'll have at least some interested folk, whether you're new or not. Presentation, of course, also helps a ton (I've become so visually-dependent that my mind shrivels up without A E S T H E T I C S to keep me engaged), while I'd say that branding your RP as based off something else (rather than just being inspired by it), is a double-edged sword in terms of getting people's attention. Pretty sure others make better points about it than I did though.

Also maybe someone already ninja'd me on these points too.

Oh well, at least I shilled.