Tip for January 2006:
Scenery Adhesive

To hold down coarse groundcover (stones, twigs, etc), use a mixture of 50% water, 50% white glue (like Elmers), and one or two drops of dishwashing detergent. Pour the mix into a spray bottle, and spray onto your scene. It forms a nearly invisible bond that holds far better than you might expect. Just make sure you are finished with whatever you want to glue down before you spray it. When the glue dries, you can not move individual rocks etc. without damaging surrounding scenery.