Great advice As soon as I started "writing professionally", I got the worst case of writer's block: basically, I felt like any plot I could think of had, quote, already been done, endquote, and wasn't original. It completely stymied me, to the point where I let go of that dream and went back to working a day job.
Thanks Amaroq.
That is why I found the 'break the routine' model so effective. It's basically a tool you can use when you aren't feeling creative. It means you don't have to strive to come up with a truly original idea off the cuff, which is a blessing when you are feeling flat and uninspired. It takes the pressure off you - in a way it feels like you are getting your ideas from someone else.
Once you are comfortable with the basic idea you can then 'break the routine' more and more creatively. You'll note in my examples above, each of 5 different ideas broke the routine in a different way. I could have come up with 5 same-y ideas (the princess is secretly the dragon; the dragon is secretly her father; the dragon is actually the Princess's twin sister; the king's wife is actually a were-dragon; the player is a dragon, but doesn't know it, etc) but when you force yourself to find different ways to break the patterns, your imagination really begins to take wing and 'good' ideas really start to flow.
The first step is not to limit yourself to simply breaking 'the narrative' routine. There are so many different ways you can make something mundane interesting. Any area which bores you or your players, anything which is stale and ordinary, is a routine to be broken. It can be a subtle break. It can be a massive break.
So, if I were to break the routine
setting of the princess and the dragon story in a simple way, I might eschew the 'Knights and Shining Armour' era in favour of a story set in the dark ages, where the Princess is no more than a feudal lord's illegitimate daughter, and the dragon just a massive worm whose lair is the riddled intestines of some dead titan from an earlier age. Or for more radical '
setting' breaks, I might make it about a princess of a Zulu tribe, or a gnollish princess, or even Princess Leia!
Another way is break the routine is to change the concept a little: maybe the story is about a Dragon which has been caught by evil humans. Maybe the dragon is a 'Paint Dragon' that has taken up residence in a massive landscape on the mural behind the King's throne. Or maybe the Protagonist is the princess, and she needs to rescue everyone else as they have been sucked into the black Belly of some stellar Dragon.
Or I might pick a routine character, and change them. Or put a moral dilemma where there wasn't one before. Or add an unintended consequence to the saving of the Princess where it was previously happy ever after. And so on.
One thing that is important to remember, though, is that you need to establish the routine before you break it! The routine is the foundation which forms the basis of your creative surges and is the part of your story which is recognisable and reassuring to your players. To put it another way, if you have no routine, there is no level of expectation to be broken, and no resonance for the players. So even though some of the examples above involve quite radical 'breaks', the stories are still recognisable at a basic level as the 'princess and the dragon' stories.
The more you play against expectations the more suspense you will build in your game. As long as you choose things that are sensible for the situation you really can't over do it. And if you never pick the cliche'd path, at some point picking the cliche is itself a surprise...
..You can even do this to avoid lulls and pauses in the game.
Yes, it's very important to remember not to draw ideas from right outside of the circle of expectation! You haven't been given a licence to be totally wacky and 'out of the blue'! That is not to say that you can't do something unexpected, but you don't want the players to go "WTF? Where the hell did that come from?" or to be looking at you nervously, so terrified of what twist you might throw at them that they can't relax. You can get away with bizarre 'breaks' very occasionally for shock value - the spaceship scene in Life of Brian comes to mind - but for the most part, any twist should totally make sense after the fact (even if it is in a slightly odd way).
As markq suggests, it's not just limited to prep time either. Get used to the technique, and you can do it on the fly. For me it's now more than a creative tool; it's a way of life. I only want to write a play, write a story, or run a game that is in some way different, or out of the ordinary. Otherwise, what is the point?