Since the OP is new I'll just point out that if you haven't paid the gratuities as part of you cruise fare they will be charged daily to your onboard account. These gratuities cover room steward, dining staff, butler (if in a suite) and other behind the scenes staff.
Tips on drinks are automatically added to each drink. If you have a drink package the tips are included in what you paid for the package. If you order a drink over the package limit you will be charge the difference and 20% of that difference will be added to the slip you sign.