This is the way it works from what we could tell upgrading on our January cruise. First of all, they have 3 categories of regular staterooms. Cat 10-12 are grouped together as "inside", cat 8-9 are grouped together as "outside" and cat 4-7 are grouped together as "verandah" (I THINK this is the case, though cat 4 might be it's own category since it costs so much more than the rest.) They have a price chart that basically tells you how much the upgrade is from inside to outside, inside to verandah or outside to verandah.
They have a separate chart for upgrades in cats 1-3. They are all based on being in a verandah cabin and I am not sure if they discriminate between cat 7-4 as far as price goes. If you want to upgrade to a cat 3 from something lower than a "verandah" then they add the cost to upgrade to a verandah to the cost to upgrade from a verandah to a concierge. I hope that makes sense.
On our 7 day cruise we upgraded from a cat 11 to a cat 6 for $698 for two people. We had a choice of a cat 6 room or a cat 5 room, but the location on the cat 6 room was slightly better so we took that one instead. The price would have been the same for cat 5 and cat 6. Just for kicks we asked how much to upgrade to cat 3. It was another $1,000 or so (so around $1700 for an upgrade from cat 11 to cat 3). We decided not to spring for the extra $1,000 although it would've been a great deal if we had (we would've ended up getting a cat 3 on a 7 day cruise for 2 adults for under $3,000 total, which is about 50% off the brochure price).
I also remember someone on the boards posting that the cost on a 7 day to go from a cat 9 to a cat 5 (outside to verandah) was $398? Going by fuzzy memory. Hope that helps.
And to answer the "how to do it" yes, you shoudl be one of the first people checking in. The upgrades available on our western did not take very long to disappear. There was also a sign up saying that the ship was full and there was no changing of cabins but we asked anyway and were glad that we did. If they have the sign up it might be worth it to ask anyway.
Lisa