"How do I do it?"
Open the avocado and remove the pit from the center. You can eat the fruit of the avocado, it's yummy and is full of nutrients!*
Wash the avocado pit under cool running water, you don't need soap to clean it. With your fingers gently wipe away and remove any of the green fruit that might be on the pit. Rinse it well and then blot it dry with a paper towel.
Carefully push three toothpicks into the thickest width of avocado, you want to push the toothpicks into the pit about a 1/2" deep. (It's okay if you push them in deeper or even a little less) The toothpicks will help suspend the avocado pit in water and keep the top part of the pit in fresh air and the fat base of the pit under the surface of the water. Be careful pushing in the toothpicks, they have pointy edges and could hurt if they poke your hands, it's all right to ask a grown-up to help with this.
Suspend the pit over a glass filled with water....the toothpicks will rest on the rim of the glass and hold the pit in place so it doesn't sink to the bottom. Always check the water level in the glass and see that the water is covering the fat base of the pit by about an inch depth. If the water is below that level you'll need to add some more. Slowly and carefully pour in more water from a small cup to avoid splashing.
Place the glass in a bright windowsill. In about three to six weeks the top of the avocado pit will begin to split and a stem sprout will emerge from the top and roots will begin to grow at the base.
When the stem grows to about five or six inches pinch out the top set of leaves. In another two or three weeks new leaves will sprout and their will be more roots.
It's now time to plant the young avocado tree. Place enriched potting soil in a large flowerpot (maybe 8" to 10" across). Fill the soil to about an inch from the top of the pot. Make a small depression in the center of the soil and place the pit, root-side down into the depression. Don't put it too deep...you want to have the upper half of the pit above the soil line. Add some more soil around the pit to fill in any air holes by the roots and then firm it into the soil by gently pushing the soil around the base of the pit. The tree's stem and leaves should be straight and pointing up (like a flagpole).
Give the soil a drink to water the pit. Water it generously so that the soil is thoroughly moist. Water the soil slowly and gently so that when it's poured in it doesn't gouge out holes in the soil. Keep your tree watered but don't let the soil be so moist that it ever looks like mud.
How do I care for my avocado tree?"
Keep your tree in a sunny window, the more sun it gets the bigger it will grow.
Remember to give it frequent light waterings but don't let the soil get muddy. If the leaves turn yellow it means that the plant is getting too much watering, let the tree's soil dry out for a couple of days, then return to light waterings.
When the stem grows six more inches pinch out the top two sets of leaves. This will encourage the plant to grow side shoots and more leaves, making it bushy. Each time the plant grows another six inches pinch out the two newest sets of leaves on top.
"Can my avocado tree ever go outside?"
Yes it can go outside in the summer. If your winters are cold ~ below 45 degrees (F) or 7 degrees (C) ~ you must bring your tree inside for the winter. Otherwise, if your winters are cool and mild, the tree may stay outdoors year round.
"Will my tree ever grow fruit?"
Sometimes they will begin setting fruit after they are three or four years old. It helps to have several avocado trees growing together to aid with pollination.