Punishments need to be personal and specific to both the person and the situation. It is no good beating a masochist - a true masochist finds pleasure in pain and so are being rewarded not punished. I generally advocate using your initial negotiation before you start a relationship to put together a list of punishments and rewards based on what the sub says are their hard limits, soft limits, likes and dislikes. Some take this further and have complicated contracts with lists of misdeeds and the appropriate punishment.

For pretty much any sub, though, ignoring them is the best method. Get them to sit in the corner, facing the wall for a period of time. Stop playing, take off the sexy clothes you may wear for sessions and dress normally. Tell them that the play session you had planned that evening is now cancelled. This is a true punishment of misbehaviour because by being punished they do not get what they want. Often a sub will play up in order to get attention and a punishment they like.

Of course there needs to be a distinction between genuine punishment and 'play' punishment. Sometimes a BDSM couple will jokingly talk about bad behaviour needing a spanking or similar - thats basically BDSM flirting.