One of the things I’ve found myself carrying around these days is a sketchpad.
The reason is simple: I have a lot of ideas, for both the companies I advise and for my own startup ideas. I’m a visual person when it comes to developing products, so I’ve always found a sketchpad to be immensely useful for drawing out the product and user engagement flows for my ideas.
When ideas get more structured, I bust out OmniGraffle, one of my favorite apps for Mac and iPad. Most product people already know about OmniGrafflie: it’s a great way to build visual product roadmaps and mockups. If you aren’t using it, I highly suggest it.
The point I’m trying to make isn’t that you should carry a sketchpad around with you. My point is that you need to have a way to immediately record and expand the ideas in your head. You can write out a story, record a voice note, start a Wiki, call your co-founder, or mock something up in photoshop. Use the medium that suits how your mind works.
In my case, I use sketchpads and whiteboards. They are my canvas. Make sure you find yours.