I stick in 6 or 8 pre-stamped postcards, addressed to me, with the box stamp impression already on it, with the message: "Please add your stamp and send me a note. Is the box in good condition?" This is to help you gauge the traffic, and if the box is standing up to the rigors of its existence. And, it gets you a few nice stamps while you are waiting for the book to fill up.

For the newbies who chance upon a Letterbox, I also stick in a sheet called "About Letterboxing"   Make several copies for them to take and include the Smithsonian article reference (April 98) and the other Letterboxing  web sites.

Finally, I place everything in plastic zip-lock freezer baggies, just in case (The Prayer Rock Letterbox has already been through one flood).   A sandwich baggie will hold the notebook and stamp, another will hold postcards and small reference sheets. A larger size (freezer bag) will hold a sheet of typing paper, trimmed a smidgen at the top, if you use larger type, although you can also print it smaller (1/4 sheet size) and get it in the sandwich baggie.

That's all there is to it. This hobby is evolving - as you get further into it, you surely will develop your favorite ways of doing things.  Please share your experiences with us.  Enjoy!