Carry your Sketchbook. Always.

Unless you're already printing up business cards and pamphlets for conventions, you should always have some example of your drawing skill on hand (if not for everyone else to see, then to give you something to do once the batteries on all your other electronic toys run out), so keep the sketchbook nearby.

For best results, make sure it's sturdy, tiny, and personalized to hell on the exterior. I prefer Moleskine, but that's because they have heavy enough covers to not require a lot of support, they're self-fastening, and they can also hold onto incidental papers (like tickets, reciepts, money... if it's paper, it'll do) in a pinch. You'll probably take a year or two to fill one of these up, so the durability will be well worth it. Don't worry about the paper thickness unless you're dealing in things like Sharpies or watercolor.

Take it everywhere. Use it for everything. Some of the more interesting pages in my books are where pencil sketches have been covered up by physics notes in ink. If you don't know whether or not you're doing this right, you're not doing it enough.

You have to do something when you're not in front of a computer, right?