Thin Bodied Paper: Thin is best for this technique using such paper as newsprint or copier paper
Wax Crayons: Wax crayons work the best, but you can also try pencil, pastels, oil pastels, and crayons
Low Tack Tape: This is used to hold the paper in place
Permission: It is best to ask permission before doing a rubbing on a public or private item. This is especially important for older tombstones/headstones. You can damage crumbling stone during a rubbing.

Clean the surface you wish to rub by gently wiping with a paper towel and water. Do not use soap of any kind on public or private property.
Cover surface with thin paper and tack into place with tape.
Hold rubbing tool (crayon, pencil, etc.) almost flat against the paper. Pastels need to be flat on the surface.
Gently rub over the image until outline of image or words starts to appear and continue rubbing until you've covered the entire area you wish to rub.
Finish with a fixative or sealant if desired. Pastels require a fixative or the chalk will rub off over time.

Additional Information

The image is rarely crisp, clear or clean. That is the nature of rubbings.
You can "clean up" the rubbing with an art eraser. Most experts recommend a knead-able eraser for the job.
Experiment with color. Do a black and white rubbing, and then do it with a single color, then one with several colors.
Pastels effect is a bit murky and more smudged. Pencils are crisper while crayon appears more solid. Again, experiment with several of the mediums.
Rubbings make great background papers and also serve as memorabelia.