Trees are available from many sources.
While mail-order or catalog sources may seem convenient, ordering from them can be risky since you can't see the product, and trees sent by mail are often small in size. The tree's root ball should have some moisture, and the leaves shouldn't be drooping or yellowing. Pruning may help sometimes, but the shape of the tree will probably stay the same. Ask the staff if the tree you're looking at has any known problems or undesirable traits, and be sure to ask about improved varieties of trees that have been specially developed to have fewer problems than their previous counterparts. They offer shade and ornamental, colorful foliage in the fall, then go dormant in the winter.