Avocado trees are easy to get started from seed. Simply suspend them over water, and soon you will have roots and leaves sprouting out. Alternatively, you can skip this step and purchase a tree from a nursery. Either way, you will need to know how to transplant it pretty quickly, as avocados grow much better in the ground. Try to transplant avocados to their permanent home by the time they are two or three years old, or you run the risk of damaging the sensitive roots.
Prepare the spot where you wish to plan your avocado tree by digging it up well to loosen the soil. If you have hard soil, add plant material such as composted leaves and grass clippings so that the area is soft and workable. Remove enough dirt to form a hole large enough to hold the root ball of the tree.
Set the avocado tree on its side and carefully lift off the container from the root ball. Be careful to leave as much dirt around the roots as possible. Place the tree in the hole so that it is centered and sitting up straight.
Add the soil in around the root ball gently without packing it down as hard as you would with other trees. Avocado tree roots are too tender to handle roughly and have a successful transplant. Pour water into the area to settle the tree in place and remove air pockets around the roots. Add enough soil to level it with the ground around it.
Mulch around the base of the tree with a loose wood bark mulch or leaf mulch to keep the surface roots cool and moist. Fertilize with a dilute general balanced fertilizer (10:10:10) over the soil 1 foot out from the trunk. Add lime if the soil is not close to 6.5 or 7 in pH.