Welcome to Cruise-Chat! On a first time cruise, use the cruiselines excursions. Once you've been to the ports a time or two and know your way around you can explore other options for future cruises. I would never advise outside excursions to first time cruisers. You can however book them in advance or book them onboard at the excursion desk if you want to ask the staff questions about the options, times, cost and other paticulars of each. Better to be safe than sorry for a first time cruise.