Most trees are adept at supporting themselves, but, because you want twigs and branches to grow in a certain pattern, you'll need to tie the branches to something.  The most efficient support can be easily constructed by sinking two stout posts into the ground at least eight feet apart.  (Width will vary depending on the shape you want the tree to take.)  Stretch 14-gauge wire at one-foot intervals between the posts.  Be sure the trellis is at least one foot away from the house or wall to allow you plenty of working room in back of the tree.  Steady the posts by connecting them to the house with metal brackets.