Joining an RP for me is something like this. I usually don't get a "craving" (ew) for something. Normally I'll see something floating on the forum, or will see people discussing something on one of the many discords that I am on. If I see a title enough times, or see that an idea has enough interest. I will check it out. I typically don't join an RP during the interest check phase, less its something I got invited too or something along those lines. From there I just look at the OOc and see if the GM has put the require amount of effort in, who else is joining, if the RP is promising me something I'm interested in, etc. I do not consider myself picky, and will join whatever interests me. The biggest deal makers/breakers are the people participating. I can enjoy various writing levels, genres, and GM styles, but people are the more irreplaceable and less malleable part of an RP. I'd rather collaborate with someone who uses English as their second language and has a great personality than an insufferable person with an English major. 

Though I enjoy control, so I usually appoint myself GM of a RP instead of joining one. There's usually very little difference between my interest check and my OOC. I believe that people are more likely to stick with an RP if you let them know exactly what's in store. It's hard to be disappointed if you know what to expect. So far that's worked very well for me. As for how I get players interested in my projects, it's a mix of luck and research. If I want to make a particular type of RP, I read up about the genre so that I can insert all the appropriate tropes and know where I can let my freedom run wild. This goes for anything from fandom RPs to original content. Original content you want to be more focused on the genre and the sort of things that make it work. While you also want to do that with fandoms, you have to be a bit more focused on that particular media and really understand why people like it. The luck comes in with the crowd you attract. The characters that get made and the players that join play a big role in your RP.