For the past 6 months I've been using a Moleskine Memo Pocket book (large size) to carry around 3x5 index cards with notes and action items. This is similar in concept to the Hipster PDA, just with 6 pockets instead of a binder clip. I've organized the pockets as follows:
Pockets are labeled: In, Actions, Someday/Maybe, To Elsewhere, Trash, and Blanks. The follows the "Getting Things Done" paradigm. 3x5 cards that need further review go into "in." Those with actions already attached go straight to "actions." Action items (or ideas) that aren't especially important, but important enough to carry around, go into "someday/maybe." Items needing filing at home go into "to elsewhere." When I need to trash a card, I stick it in "trash" because I generally want to recycle the card at home or shred it. And of course the "blanks" pocket holds blank cards.
This system has worked pretty well. I use it mostly for my personal action items, but also for work when I travel. (At work I have a desk-based setup.) If I'm at home and I have a work idea, I jot it on a card and put it in the "to elsewhere" pocket. The only trick is remembering at work to go through the "to elsewhere" pocket and pull out work-related stuff. Likewise, I often forget to pull out items for filing when I'm at home.
Another variation on this idea would use the pockets in a location-based manner, e.g. label the 6 pockets:
- @ work
- @ home
- @ computer/net
- @ phone
This is perhaps a more purist GTD approach. Using this system, when you get to a location and start doing work, you first dump that pocket's contents onto your desk. This prevents you from having to sort through the "next actions" cards looking for actions that can be done now.