Game Development Manifesto v.1.0
Spend more effort prototyping gameplay than doing market research. (My friend Ethan adds: Putting a prototype in front of a player is the only market research that matters.)
Designers need the ability to easily and quickly test tweaks from day one.
Before you have two engineers you need to document a coding standard and a branching strategy.
Before you work on a real feature you need source control, automated builds, and push-button deployment.
If you are ever going to localize you should build the framework before you complete a single user-facing feature.
Figure out your art and data pipelines before you add any art or data. (Once the pipelines are in place engineers should not be required.)
Figure out how to add and remove assets without breaking the game.
Figure out how to do non-ugly screen transitions before you show the game to someone outside the dev team.
Don't use new technology unless that's the only new thing about your game.