Flow Chart

1.Brainstorm all game formats( 2D, 3D, tile based, scroll based, turn based, action based )
2.Then think of what is the focus or focuses of the game
3.Match what formats fit with the focus
4.Brainstorm what could be included in the game
5.Start programming small parts of the ideas you brainstormed
6.As I program, I think of other ideas, as well as, how to focus further into the game and which formats are in the best interest of the game.
7.Start programming the very base of the game
8.Brainstorm ideas that will be used in the game and choose the best one
9.Program that function
10.repeat step 8 and 9 until you are done the game

I find it easier to brainstorm a little bit, then start programming every aspect until I fully know what I want. It is never a good idea to fully plan out the game as things change and it is also much more difficult and inefficient to program top down then bottom to top. It is easier to think small and program small.