<human>:  How do I prune a tomato plant?
<bot>: Pruning tomato plants is a important part of plant care. The best time to prune is when the tomato plant is still young and only has a few branches. Prune off excess branches and stems that are growing downward, as well as any withered or dead branches. Make sure to prune only 1/3 of the healthy branches, and prune back each branch to at least two sets of leaves. Avoid pruning off all of the buds (which then become flowers and fruits) as this will reduce your overall yield. Lastly, make sure to use sterile, sharp pruning shears, as this will help prevent any disease or pest infestations.