First lesson, though I learned it some time ago, is write down/sketch/draw any idea that gets into your head! I have lost a few already, despite it being a lesson learned some time back. That being said, you have to be flexible and just go with it.
So far, I have sketched out to some degree all the characters I intend in my film. I have set short term goals and milestones.(the timer really helps there) The story has been written out in full and I am presently working on storyboards and dividing it into scenes. I am really focusing on keeping it simple.
With every scene I am always addressing the questions:
-Is it crucial to the story line or is it just filler/superfluous?(a bit of comedy relief is fine I believe)
-Is it easily animated and rendered? Does it require learning something new(a special effect, etc)
-Does it keep the flow going? Last thing I want is a too simple movie that is dead and boring!
-Am I over complicating or making the scenes confusing. If it is very confusing for me to put together while editing, etc, It will probably be confusing to watch.
With all that to consider in each scene, I have started to do likewise with the characters I have created. I can start to pare them down or add more detail to some, as to how they will play out in the movie. Last thing I want is to create a character that I have to remake because I added to much detail or the rigging demands prove too much for the detailing I have done!
Of course, to many people out there these guide lines are like second nature. But when time is short- one needs to focus on only what matters. If there is time tp spare, then I can always go back to it!