It might sound dumb, but please bear with me.....
When you are out & about carry with you...at all times...a simple pen and paper. "Of course!", I can practically hear a lot of you saying this out-loud, but I want you to think about the more-than-likely many times you needed a pen to make a note, sign a credit card receipt, whatever...and didn't have one. In my experience a pen is much more common for people to have than an appropriate thing to record some notes in.
What I'm deliberately advocating is that you start carrying a pen and paper with you everywhere you go. Not just any pen & paper either, but something you've specifically dedicated to this pursuit. Designate a good everyday carry pen and a specific note-pad. Keep them wherever you keep your wallet & keys and start taking them with you when you leave the house.
I love the model 400BCL) and I've been using one of a trio of Munchkin notepads I picked up at Origins last year. I do have some smaller & way cooler moleskin notepads that I could fit into my wallet, but I was finding I myself reluctant to use the smaller format for some reason.
The thing is a good idea can be fleeting and you never know when you'll have another one, or if you can remember the ones you've had. Heck, even bad ideas can have some value!
Start carrying a dedicated pen and paper with you to jot down ideas as they come to you. I guess you could also use these to write down non-GM/gaming information, but that's just be a bonus I guess.
|Example of a quick idea to finished concept|