David Letterman's Top 10 list would never cover gardening methods. If it did, it'd probably be an hour-long segment and would appear on the Home and Garden channel. So putting it into type and shortening the list a little, here's the Top Eight List of things everyone should know about trees (Source: The National Arbor Day Foundation; arborday.org).

8. Remember their roots!
   Roots like oxygen-laden soil and won't grow in the compacted, airless soil beneath streets. Roots tend to grow outward up to two times the height of the tree, and 8-12 inches below the surface.
7. How to plant free-rooted trees.
   A few quick steps:
   1. Unpack the tree and soak it in water for 3-6 hours. Don't let them dry out, and don't plant the tree with packing materials attached.
   2. Dig a hole that seems larger than needed to let the roots grow. Remove the grass within a 3-foot radius and turn the soil.
   3. Plant the tree at the same depth as the nursery where it was purchased. Partially fill the hole, without soil additives, and pack the dirt firmly, but not tight, around the roots.
   4. Shovel the remaining soil in and pack it with your heel. Make a water-holding basin around the tree and give it plenty of water.
   5. Once the water soaks up, place 2 inches of mulch in a 3-foot radius around the tree (not touching the trunk), and water the tree generously every 10 days for the first year.
6. How to plant contained trees.
   A few more quick steps:
   1. Dig or rototill a hole one foot deep and about five times the diameter of the root ball.
   2. Keep the soil around the roots, and only handle the tree by the ball (not the trunk or branches). Don't let the ball dry out.
   3. Prevent girdling by cutting roots that seem to circle the root ball.
   4. Place the tree in the hole and pack the soil firmly (not tight!) around the root ball and water it.
   5. Place a 3-foot radius of mulch around the tree (not touching the trunk).
5. Don't forget the one-third and one-fourth pruning rules!
   When pruning a tree, don?EUR??,,??t ever remove more than one-fourth of the tree's crown in one season. If it is possible, encourage branches that form angles one-third off the vertical position, or at 10:00 and 2:00. Most species of trees should have only a single trunk, and ideal main branches are only one-third smaller than the trunk's diameter. When you remove a main branch, don't leave a stub; cut the branch all the way to where it is attached to the tree. Finally, don't prune deciduous trees up from the bottom any more than one-third of the tree's height.
4. Don't just hack off a limb!
   On a larger limb, make a partial undercut about a foot from the trunk, and a second cut on top of the limb a few inches away from the first. The limb should just fall right off. Then go ahead and take off the stump at the base. Smaller limbs should be cut, at about a 40-degree, sharp, clean cut just above (but not too close!) a lateral bud or another branch.
3. Got mulch?
   Mulch retains moisture, insulates the soil, deters weeds, prevents the soil from compacting, and reduces lawn mower damage. To mulch your tree, remove the grass 3-10 feet in diameter (depending on the size of the tree) from around the trunk. Then fill in the circle with 2-4 inches of mulch. Don't let the mulch touch the trunk.
2. Death by Girdling
   Girdling is when most of the bark is removed or injured around the circumference of the tree trunk. Often, this is caused by lawn mowers or weed trimmers, and it destroys what is akin to the veins of the tree. Minerals and water are unable to reach the leaves of the tree, and food made in the leaves is unable to reach the roots, starving the tree.

1. Don't top the poor thing!
   Topping trees to keep branches from phone lines and such not only makes them look ugly, but it's probably embarrassing for the tree! Branches will grow back higher and with weaker attachment. While the tree is bald, it can starve because it is not getting food from its leaves. It is also more susceptible to insects and diseases, and we all know there are plenty of those going around!