I keep a small note book in my golf bag for taking notes, or just writing things down that I want to remember later. I get some of my best idea while tramping around a golf course. The combination of fresh air and exercise are good for the brain.
In the past I’ve used a Moleskine, but as that is filled, I think that I may go to one of these indestructible notebooks. The Indestructible Field Notebook is waterproof, tearproof and weatherproof.