Room upgrades?

Hi,
I have read a lof of reviews where people talk about getting upgraded once they board or what not. Is this common? I assume it depends on space available. How does one do this?

Thanks

Jay

[Brenda in Canada]

I am hoping for the upgrade fairy to visit us too!! I think it depends on how full the ship is, which category is full etc. and people book a Guarantee room(IS,OV,Balcony) hoping for an upgrade. I do not think you get upgraded as often from one category to the next. But hey!!-you can always dream of a magical upgrade fairy!! Do as many people with specific booked rooms get upgraded?/not sure. People with more experience should be able to give more ideas on how it works.