From the very earliest of casinos, and even dating back to the card tables of the wild west etiquette among gamblers has been used to avoid confusion over wagers and to eliminate (or at least reduce the risk of cheating). Craps as we know it today was brought to American from France through the ports of Louisiana in the eighteenth century. With the game came the etiquette.
Rules regarding handling of the dice have certainly been around since the beginning of the game. For instance, to reduce the risk of switching the dice with weighted or 'fixed' dice, players are expected to handle the dice with only one hand, and it is definitely forbidden to switch the dice between hands. Also, for fear of changing the dice, players are forbidden from carrying the dice past the edge of the table. When throwing the dice, players are required, generally, to throw the dice hard enough that they strike the far wall and bounce back to avoid a calculated throw.
Food, drinks, and cigarettes are all strictly forbidden from the craps table. Anything that could affect the roll of the dice is definitely tab boo. Even if not stated, if a dice should stop while leaning on the object, the number that is used is the one that would be shown if the object were removed.
In online craps the etiquette can be convoluted and at times esoteric. Part of the problem with online gambling etiquette is that players from all corners of the world come together and mix their ideas of what is acceptable. To get into more detail about what is acceptable, read the guide posted on Dwight Painter's blog about online craps casinos .
Some items of etiquette are simply based on superstition. For instance during a round after the come-out roll it is considered bad luck to say the word seven. Instead, if one should need to refer to the number seven. they should use the term "Big Red". Under no circumstances should an experienced player change the dice mid round. Even if a dice should fall from the table, after inspection from the box man, it should be returned to use.
Regardless of origin, etiquette for craps (and all casino games) should be fully understood before ever entering into play. Consequences from breaking etiquette are commonly limited to a warning or just criticism from fellow players. In more severe cases players may find themselves being removed from a given casino. All players are well advised to fully understand basic etiquette, and as always please gamble responsibly.