This idea was part Catt's, part mine. When she is looking at a magazine, and she sees a recipe that she likes, she'll tear out the page(s) containing the recipe rather than keep the whole magazine. Or, she'll cut out the recipe if it's small.
The result was a pile of snippets and pages, so I tamed the pile by hole-punching the whole pages and sticking them in a binder, then taping the snippets to either a full size sheet of paper that I hole-punched, or to an index card. I know that a lot of people intend to write the whole recipe out on the index cards, but who really has the time for that, especially if it's one that you haven't tried yet? Taping it to the card works just as well--you can wrap it around the side of the card if it's a long snippet.
The next step is to keep track of the ones you try. If it's a keeper, move it to a different binder marked "Keepers". If it was indifferent or crappy, rip the page out, throw it in the recycle bin, and be done with it.
Also, if you're trying stuff out in a cookbook, feel free to take a pencil to that sucker. I am merciless with my cookbooks, marking the recipes in a star-rating system, and commenting with adjustments or alternative ideas. I can never leave a recipe well-enough alone, so making notes right in the book helps me keep track of what I've done, what's worked, and what I shouldn't bother with again.