The etiquette of asking for a raise is exactly like the etiquette of asking for anything else. Since money is a measure of value, and since value is fluid, timing is everything.
Approach your boss to open negotiations at a time and in a setting that places your boss at ease, preferably when he is flush with a new contract and already thanking you for a job well done in getting it and not after its too late and not right after the company releases bad earnings numbers.
Modified from HOW TO ASK FOR A RAISE
