Stopping/pinching out/nipping back are all colloquial terms meaning the removal of the growing tip from the stem and then consequent stems) to obtain more branches.It is not my intention to try and confuse you or over complicate the issue by extolling the virtues of stopping a plant for exhibition purposes, that can come later, however, to obtain bushy plants you must stop them This can be done at any stage when the plant is growing steadily in a minimum of a 2.5" pot.
Let the plant have at least three pairs of leaves and a growing tip before the first stopping commences otherwise you lose the branching effect. Before carrying out the removal of the growing tip it helps if the plant is turgid (watered to you and me).
To remove the growing tip you can use a sharp knife, razor bladea, pair of small scissors or do what most people do, use your thumb and index finger nails, I would suggest you refrain from the later, but if you are going to do this push the tip to one side and it should snap off..
Whichever method you use be very careful not to damage the young growth coming from the leaf axils (these are at the node, where the leaves join the stem).
