When I began creating this new game, a few ideas quickly formed in my head about what to make; the theme, the genre, the characters etc. The first thing that I did was spend a day going through the 2D sprite sheet tutorial that I posted previously. After I learnt the basics I had a running man who could jump, I suppose that is the beginning of many games. I continued with my original idea; a kind of side scrolling doodle-jump amalgamation, until I round myself into the ground with complicated jumping and landing mechanics, at which point I deemed that which I was doing too complex for to achieve with any ease. That evening my head was full of bits of games I could make, half ideas I was sure would work for all of 10 minutes.
The following day, I, with the help of glamorous assistant (my girlfriend), brainstormed all of the ideas I came up with up previously. This allowed my thought processes to come together and think more clearly about what I wanted to do.
This is that brainstorm, and you can see the ideas that I had for the different elements of the game. What came out of the brainstorm more than anything was a basic idea of what the game would become; the themes and genre etc. As we went through each section, a much stronger idea began to form of what game I would make, and it began it sway my decisions about what I wanted it to be.
Even so, having an idea and knowing what to make are two very different things, the next key part was when I told my girlfriend what my idea was. She questioned the parts that weren’t clearly explained, meaning I had to think about them more so I could explain my vision coherently to her, and this meant that I understood my own ideas with greater clarity. I think that it was this explaining that has been key to speed of the development of the game, going from non-existent to working at a basic level in 2 days. From now on I will be spending time before coding talking through my ideas with friends/family/peers so that I can clarify them in my own mind and make a better game at the end of it.
TL:DR; diving head long into development is dangerous, brainstorming is good, talking your ideas through with people is better.