Begin pruning or harvesting the red basil plant from the leaves at the top of the plant, down. This keeps the size in control and prevents the plant from becoming top heavy.
Follow the stem of a fully grown leaf back to one-third of its length, or to where the stem intersects with another set of leaves. Make your cut at that point with gardening shears -- or pinch with your fingers. Regular harvesting encourages the growth of more leaves and discourages the plant from going to flower.
Cut off any flower stalks the red basil begins to produce with shears or by pinching back with your fingers. Once flowers are growing, the plant may slow the growth of the leaves, so it is essential to remove the flowers as they appear. Cut the stalks off at the base.