In my view, punishment serves two main purposes: 1.) to ensure there isn't a repeat incident of that action; and 2.) to ensure the submissive knows what they did & why it was wrong. Anything beyond those parameters, in my view, make it less punishment & more something else...
Everyone deals with misbehavior in their relationship differently. First off, as several have suggested, there is a difference between actual misbehavior & something like "brattiness," which isn't actual misbehavior, it's just acting up/out to get a desired response from the Dominant. And often that "desired response" includes spanking, etc. But let's call it what it is and not punishment. Because calling this type of response punishment tends to confuse folks & often leads to a blurring of the definition of punishment, and, in turn, to the blurring of lines between acceptable & unacceptable behavior. It's the Dominant's job, imo, to ensure that the lines of what is acceptable & unacceptable are clear to both the Dominant & the submissive. Bratty behavior to illicit a particular response is "acceptable" behavior, as the Dominant doesn't really "punish" the submissive, but actually doles out a programmed response that the submissive desires to achieve by doing that behavior.
Now, as for actual punishment (to get to Alex's point in the thread), there are different ways to punish, and no way works for any 2 submissives: you have to find what works for you & yours, and use it effectively. For some, positive punishment works the best: giving the submissive extra tasks, or a beating of some form & degree, etc, etc. For others, negative punishment works better: take away privileges, take away time/contact with the Dominant, etc. Just some things to consider...
1. Proportionality: Everyone has heard the old adage, "Don't make a mountain out of a mole hill." Well, that works for punishment as well. Make sure the punishment is proportional to the action. If it's something serious, use a more serious punishment. But be careful not to overreact: this leads to 2 different issues. First, if you overreact, the submissive is apt to be petrified about screwing up at all, ever. Second, how will the submissive ever learn what things are more important then others?
2. Communication: This sort of feeds into proportionality... but do be cogniscent (sp?) to make sure you communicate why the action was wrong, how to fix it for next time, and exactly what the punishment will be. There is nothing worse then not knowing why you are being punished. Also, submissives WILL screw up (*gasp* I know! shocker!)--it's just part of life. The submissive needs to feel that they are loved & cared for, and that sometimes, punishment just isn't what's needed: the submissive will have beat themselves up enough, or maybe it's just something minor that requires a fix & talk, rather then punishment.
3. Time it Right: Much like a child, a submissive's transgressions come often at awkward times in awkward places. When possible, punish right away: the incident is fresh in both of your minds, and the punishment will then be over & you can both move on, so that neither of you dwells on it for hours or days. However, sometimes you can't punish right away: either the Dominant needs time to lower their anger level, or you're in an inappropriate setting (hellooo public), or it's something that the Dominant wants to think through before doling (sp?) out. In any case, timed wrong, the punishment ends up doing more harm then good. So it's something to think about.
4. Never punish when angry: This goes for both the Dominant AND the submissive. Never punish when you're angry!!! It leads to nothing but more harm. Take the time to cool off. If you're the Dominant, just say "I need space." Just be careful to not act out of impulse, but rather, act out of rational thought. You will regret being angry & impulsive in a day or two, but the damage that occurs can last forever. I knew of a Dominant that was so angry he beat his submissive to such a degree she had to go to the ER. Again, be careful & safe.
5. Know your submissive: I can't say this enough, and I say it to EVERYONE I know as many times as possible: EVERYONE IS DIFFERENT!!! And EVERY relationship is different. What works for one couple won't work for another. O/l punishments, by their nature, differ from r/l punishments: just as o/l offenses/actions differ from r/l ones. So punish accordingly. Some submissives also do better with positive punishment (beating of some form, corner time, etc.) v. negative punishment (time away from their Dominant, loss of privileges). Some submissives will also beat themselves up like crazy, others need a "talking to" and a "firm hand." Some submissives need instantanious punishment, some need to have time to think about their transgressions before they are punished. Bottom Line? Know your submissive!
6. The Result: The result of a punishment should be that the submissive knows what they did, knows why it was wrong, and BOTH the submissive & the Dominant feel closure on the incident. You can't punish & then bring the incident up again in a few days. Punish & move on. As T likes to say "shit happens." So does stupidity--so take it at face value, give the proper, proportional punishment, and then both of you can move on. How many dozens of times have I heard, "My Dominant put me on cum restriction for two weeks because of ______." What purpose does this serve? It continues to draw out the incident, it doesn't usually serve a punishment purpose (does it make the submissive correct their transgression? does it make them know not to do it again?), and it ends up turning into something that is more a hinderance then a learning experience. Get creative, find out what makes your submissive tick, make sure you are giving appropriate punishment.
As I have droned on & on, I will now hop off my soapbox...
As always, be safe & use some COMMON SENSE!