Pitching an RPG is synonymous with selling it. I stink at selling anything. Cavemen would swear off fire if I was the salesman. I've read about selling things and tried to implement tips, but it doesn't come naturally for me. So understand that I'm working through this from my own highly dysfunctional abilities.
One of the big pieces of advice that you get for selling is to solve a problem that the customer has. It occurred to me that I'm always working to solve problems in design but I never write down the specific problems I'm trying to solve. That's a big oops since those are the points that I should be talking about when trying to pitch a game.
I'm not just talking about mechanics either. Story elements are often there to solve problems, so they should be factored in.
It would be ineffective to just pepper everyone with the problems you're solving. I see this approach used frequently and I admit to trying it in the past. What a salesman does is figure out what the customer needs and then draws out the points of the product that would help with that.
Maybe I should be writing down my specific design decisions and what they do. When I try to pitch a game, I attempt to figure out what problem a player is trying to solve and figure out which design decisions help with that problem.
Another approach would be to design according to the problems that people say they want solved rather than the problems I want to solve. That sounds boring though.