Plot? Setting?
I'm not much for plot as such, but plot and setting tend to come with the basic game idea for me. And since basic game ideas claw at me constantly like the clinging souls of the damned they're usually pretty easy to get.
Rules beyond the vanilla 1d6 set?
This one's trickier.
My solution to it is to realize the current system doesn't do what I want it to or does something I don't want it to, start thinking about possible solutions to that, run with those until I realize they don't work or I don't like them or are hideously complex, and then get distracted with an entirely different project.
As for what you should try, it really does depend on what you want. I find other games, forum or video, can be very, very handy inspirations. Other media can also give less formally defined systems, where you see something you like or don't like and start to consider what kind of a system that'd be. For original creations or deciding what you want to steal, I tend to find thinking about what you want to happen or not happen can be handy, then working the system into that.
That's kind of vague, but I could probably supply examples if you wanted. A lot of it, as far as I've been able to tell, does just boil down to working on it long enough to figure it out properly. Also motivation.
General rule: take a commonly accepted game mechanic from video/forum games in your desired genre and make it even more ridiculous.
This is how inspiration works.
I was not aware of this. Hit points are now a fluid you beat out of foes or refill. Makes after-battle scavenging interesting.
Now I actually want to make this game. FFS is clearly a professor.
* Darvi points at reply #7852.
Steal harder scrub. Really though, if you won't steal, where are you willing to get your materials?