It does not matter if you are playing in a land based casino or gambling online; it is always a good idea to duly practice the proper behavior and to remember the ways to act suitably. The bottom line is to win, but that in no way does that mean you should ignore ethics.
If you are playing a land based card game, such as Poker, always keep in mind that it is also a form of social activity. If it is a home game, you should try to keep the atmosphere light. Although you will want to try and win, most of the time the games are for fun, and there is no need to feel tensed up, or even start a fight about it.
If you are gambling in a casino, you should always try to be as courteous as possible. Do not gloat when you win, nor should you sneer at a player who makes an elementary mistake on the table. You should also avoid antagonizing other players. Of course you come to the casino to win, but you should also be prepared to lose.
You do not have to be cheery when you suffer a bad beat, but gambling etiquette dictates that you should do your best to be civil and courteous.
You should also show respect to the waitresses, chip runners, dealers and the other staff at the casino. You do not need to tip them all; often a sincere thank you will be more appreciated than handing out a tip with a dour look on your face.
There are also ethical rules for gambling online. You should not abuse the chat box; a lot of people, feeling secure because of their anonymity, use it to rail against other players, or even the site itself when they lose. You should not do that, mainly because you could get barred from the site if you carry it too far, and secondly, it is just plain wrong.
The same can be said when in gambling forums. When you see someone post a message that disagrees with what you have stated, just stick to the facts. You just make your point, and if he disagrees, just leave it.
Finally, always pay up. Regardless of whether it is a home game, online or in a casino, you should never gamble unless you have the means to pay up. Remember these guidelines, and you will be able to relish your gambling experience, the way they were meant to be.