Posted on the Disney Cruise Lines web site (<a href="http://disneycruise.disney.go.com/disneycruiseline/faq/faqgroupingindex?id=RatesAndDatesFAQGrping#RatesTippingFAQ">link</a>)
You should never feel that a reward is automatically expected from you. But it is customary to give gratuities in recognition of service, which you will most likely be treated to in abundance aboard the ship. As a guideline... [Disney Cruise Lines] suggests the following:
<p align=center><table border=1 cellpadding=10><tr><td><b>Per Guest per cruise</b></td><td align=center><b>3-night</b></td><td align=center><b>4-night</b></td><td align=center><b>7-night</b></td></tr><tr><td>Dining Room Server</td><td align=right>11.00</td><td align=right>14.50</td><td align=right>25.25</td></tr><tr><td>Dining Room Assistant Server</td><td align=right>8.00</td><td align=right>10.75</td><td align=right>18.75</td></tr><tr><td>Dining Room Head Server</td><td align=right>2.75</td><td align=right>3.75</td><td align=right>6.50</td></tr><tr><td>Stateroom Host/Hostess</td><td align=right>10.75</td><td align=right>14.50</td><td align=right>25.25</td></tr><tr><td>Dining Manager</td><td align=center colspan=3>Your Discretion</td></tr><tr><td>Room Service</td><td align=center colspan=3>Your Discretion</td></tr></table></p>
[Be aware that...] a 15% gratuity is automatically added to bar, beverage, wine, and deck service tabs. [Additional gratuity, should you wish to add it, can be added on the charge slip you will be asked to sign.] All gratuities can be charged to your room charge.