The general rule for citrus is not to train them by pruning. However, citrus do sprout lanky, spiny, flowerless suckers from just about anywhere on the plant. These need to be removed at the source. If you want your tree to grow to true size, also remove all fruit that forms in the first 3 years in at least the mid- and top-portion of the plant. Finally, citrus trees planted in the ground need skirting: prune any drooping branches so that there is a 12” to 18” clearance from the ground to prevent pests and mold from coming up the tree. If you top your citrus tree to control the height, be sure to cover the spot with 50% shade cloth until new leaves sprout to protect the inner bark from sunburn -- or prune in early spring or mid Fall when the sun is not intense.
Lemons are
vigorous. I would keep the height under 8 feet. Here's some more information on feeding and watering:
http://www.plantsthatproduce.com/gui...mmonCitrus.pdf