Step two to effective roleplaying is to have an idea in your mind. If you're starting one of your own, what plot do you have in mind? What interesting twists can you add in to make the roleplay exciting? I have a bit of experience in this department as I've been in many roleplays that have been really interesting. Honestly all you've gotta do is find something that interests you (for me, it's mostly Harry Potter) and base it around that. There's an old saying that goes like this: if you build it, they will come. If you make an interesting roleplay, people will come. Sure you might have to explain a thing or two but that's what introductions are for!

Take my Kingdoms of Thavania RP for example. The main storyline is that Thavania is an isolationist, sort of dysfunctional country ruled by several kingdoms who are all vying for total control of the country. If you make an interesting plot like that, people are sure to join.