1. Get a trowel and a bucket. Be sure neither is rusty or made of galvanized (zinc-coated) metal, which could skew your results.
2. Scrape mulch and leaf litter from the soil surface. Dig out a wedge of soil about 6 to 8 inches deep, and set this wedge aside.
3. Now dig out a half-inch piece of soil from the hole and pour it into your bucket.
4. Repeat steps 2 and 3 at least a half-dozen times in different parts of the garden so that the soil sample represents your whole garden when mixed.
5. Use your trowel to mix the soil together thoroughly.
6. Fill the soil sample bag or container with the mixed soil, complete the paperwork and mail it all off to the lab.