Game design and development is all about going over an idea over and over again, making changes and improvements along the way. Really this is the same for any idea or project that I have worked on. Iteration is KING!
So you have an idea you throw it onto some cardboard and you test it yourself to make sure it makes sense. Great! Now you take your idea and walk out into the real world. After each play you are bombarded left and right with new idea's and people trying to change the game. For the most part it may seem like noise. What do you do? Ignore them and push on? Try to implement their ideas?
The importance of the pitch cannot be understated. I am no master at it, but I can relate what has worked for me over time.
When I first started, the content of the pitch was mostly about the mechanics which I thought were cool and my motivation for doing the game. This was long winded and could be rather boring