You can start with an avocado seed. Wash it. Use three toothpicks to suspend it broad end down over a water-filled glass to cover about an inch of the seed. Put the glass in a warm place out of direct sunlight and replenish water as needed. You should see the roots and stem start to sprout in about two to six weeks. (If you’ve followed this process so far and have not seen roots or a stem sprout in more than six to eight weeks, try another seed.) When the stem is 6 to 7 inches long, cut it back to about 3 inches. When the roots are thick and the stem has leaves again, plant it in a rich humus soil in a 10½-inch-diameter pot, leaving the seed half exposed. Water it frequently, with an occasional deep soak. The soil should be moist but not saturated. And don’t forget: the more sunlight, the better. If the plant turns yellow, you may be over-watering; let it dry out for a few days. If the leaves turn brown and fry at the tips, too much salt has accumulated in the soil. Let water run freely into the pot, and drain it for several minutes. When the stem is 12 inches high, cut it back to 6 inches to encourage the growth of new shoots.