For this project, you'll need:
1. A selection of stones to etch. I've found that flat "river stones" work best, since they have a smooth, fairly flat surface onto which you can etch your messages.
2. Play-doh or other type of modeling clay, which you'll use as a moldable base/jig to support the stones on the laser etching table.
3. Ruler or calipers to measure the flat, etchable area on each stone.
4. Pencil to mark the etchable area on your stones.
5. Access to a laser etching machine. I highly recommend the Trotec (and other) lasers available through membership at TechShop (http://www.techshop.ws