Tips traditionally are handed out the last night of the cruise. So on a 7 day cruise, that would be Friday night. On Thursday night, you will get l pre-marked envelopes marked HEAD SERVER, SERVER, ASSISTANT SERVER, and CABIN STEWARD. You can tip in cash, or you can go to the Guest Services desk and charge your tips, you'll get a piece of paper to put in the envelope.
I wait until the last night to decide exactly what I will tip each person, but I tend not to tip less than the guidelines. So you have lots of time to decide how much you want to tip.
Now, tips for individual drinks are automatically added to each bill, and you are expected to tip the person delivering room service at the time of service.