I’m not currently a professional Game Designer but I thought it would be handy to start a list of what are the best design principles for creating a good game. That list follows and will be built over time.

1. Keep the technology requirements of the game, what you need to play, down to the very minimum necessary.
2. The goal of any game is to make it fun and enjoyable for all involved. Game rules should have that in mind.
3. Any character action in the game should have repercussions for the character, good or bad.