Trees produce hundreds of buds, some of which develop into blossoms and finally fruit, while others form new branches.  Usually fat, bulging buds are the fruiting buds; narrow ones are leaf buds.  The key to shaping a tree is identifying the leaf buds and choosing the ones that will contribute to the espalier design you have chosen.  For example, if you are aiming for the simple tier system, a cut is made just above two buds on opposite sides of the trunk, about 12 inches above the ground (in line with the first wire on the trellis).

Then, as horizontal branches elongate, tie them to the wire with soft twine or strong cloth.  The tree will continue to grow vertically, eventually reaching the second wire of the trellis.  This is the time to select another pair of buds for the lateral development.  Remember, however, that buds have no idea what's going on and will sprout willy-nilly if not pinched back.  Keep an eye on new growth throughout the growing season.  If buds begin to send out new unwanted growth, pinch them off with your fingers.  To achieve the tier shape, plan growth so the bottom tier is healthy and strong.  Each succeeding tier should be somewhat shorter in length to balance the overall shape.

To achieve palm or grid shapes, the training procedure is a trifle more complicated because the branches will have to be gently bent to conform to the pattern.  To accomplish this, use short sections of bamboo or other wood to form a temporary horizontal support to which developing branches can be tied.  Then bend new growth to the desired direction, and tie to wood sections.