Hi Jane. One caveat to Blythe's answer is that those booked on excursions will be given priority when disembarking is by tender. Oh, and avoid taking your passport ashore unless it's mandatory. And rather than risk losing other photo ID, take a photocopy of your passport. And take your (original) driving licence ashore only if you plan to hire a motor or do a m/cycle or quadbike excursion. Have fun. Chris.
When the ship has been cleared by customs/immigation there is usually an announcement to advise you can now leave the ship and where the gangway is located. There will also be an indication as to whether you need to take a photo ID with you. The Americans use thier drivers licence we use our bus pass but sometime you do need to take your passports but less and less ask this. On return you will have to show your seapass to the security staff at the entrance to the pier where you ship is berthed. Those who are booked on excursions will have to go to a specific part of the ship, sometime the theatre and await their until their tour is called then they will make their way to the gangway as well. Make sure you take a careful note when is the last time to be back onboard before the ship sails. There will be taxis/minibuses available for hire if you want to go somewhere but not with a ships excursion. Many perfer this option as these are cheaper than the ships excursion costs but if you have not gone it along option before good idea if you meet up with some like minded passengers who have and kow all the tricks so they can pass them onto you or perhaps you share with them ? Have a great cruise.
If you are taken ashore by tender, try not to leave it too late to get back. The queues for the tenders in the last hour can be very long.