Hi Wendy. Going for a guarantee means that you are not assigned a specific cabin number at booking. Instead, you guaranteed a cabin in at least the category for which you paid. I've never done this, so I have no experience to share regarding NCL. My niece has done guarantees a few times on NCL. She once got moved from an interior to oceanview cabin, and another time she was moved from one interior cabin to another interior cabin closer to the middle of the deck.