If you are playing roulette at a traditional casino, the etiquette rules may differ slightly than if you are playing online. For example, it is considered good form to offer a tip to the dealer if you have a large win - this isn't really necessary online! Here are a few tips on etiquette for both land based casinos and online casinos:

Land Based Casinos
All bets must be placed before the dealer calls 'no more bets' and chips should not be removed or moved in any way after this. Don't touch or move another player's chips, if you wish to place a bet on the same number, it's acceptable to stack your chips on top. Bets can't be placed once the game is in progress, it's best to wait until the end of the current game. Purchase your chips in good time to prevent any waiting around for the other players - be considerate!

Online Casinos
The software for online casinos won't let you make any mistakes, such as placing bets after the dealer has said no more. There aren't any other players at the table that you can inadvertently offend and there's no way to be rude to the dealer. Some online casinos offer a chatroom that you can interact with other players in, but if you are familiar with chatrooms, the rules are usually similar. Basically, if you wouldn't say it face to face, don't say it in a chat
room. If you're playing for fun, try to keep your language moderated as there may be younger players around.

Above all, have fun! Don't play with the sole purpose of making money - there are professional gamblers out there, but it doesn't mean you have to stress yourself out trying to follow in their footsteps! Set yourself a limit and don't go over it. If you do win big, that's a great time to stop playing - don't blow it all trying to do it again.