To Harvest Basil All Summer Long.Don't let your plants develop flowers. It isn't enough to simply pinch off the flower buds (this just encourages the plant to make more buds). Pinch off the top sets of leaves to encourage the development of new leaves.
Prune basil so it stays bushy and productive On a basil plant the leaves grow in twos opposite each other. As the little plant send up the stock it will grow two more leaves. You need to go to those two leaves and prune about one inch or so above them.