Take notes, Take LOTS of notes.
I feel like this is probably common practice among designers, but I still think this is good to hear again just to reinforce the idea. Whatever you are working on, take notes, as often as you can, as you work on your games. Notes will help you make sense of what you were thinking when you come back to a game months from now. Notes will help you find your way back on track when you get lost in your design. Notes will remind you why you made certain decisions along the way. Notes will help you justify design decisions to the people who ask why your game does what it does. Notes will give you the full back story of the game and that give you confidence and the knowledge to fully explain and provide conviction to the theme and mechanic you use.
That is not the complete list of the benefits notes will provide but the point is that notes are good. Whatever you use your notes for, I guarantee you will find a benefit from keeping them.
As a personal example, one of my favorite reason to have notes is the timeline I can follow as the weeks and months go by. I date all my notes and I like to go back through my note books and see what I have worked on, where my ideas have gone and where my ideas have improved. It feels like something as simple as adding a date to a note makes me focus more because I know I will be looking at these notes again in the future and for whatever reason that makes we want to work to keep producing these notes and make them better and more meaningful. Beyond the extra focus my notes provide me, there is a great story that I can tell myself, and others, when I do go through my timeline of notes.
If you have any comments or questions, leave a comment here or email Chris at email@example.com
If you have made it this far, would you like to go a little farther? We have a regular Google hangout with other designers. We talk about the games we are working on and share helpful tips and ideas on how to make designing our game easier. We meetup every other Saturday. Either comment here or tweet me or email me and I will add you to the list and send you a link to the Google hangout.