Here's what we found on our Princess Cruise last year. We did the 10 day cruise that consisted of 3 days on land and 7 days on the ship. You have a choice of cruising up and then doing the land tour or the land tour and then cruising back. The land cruise is more hustle/bustle so we elected to do that first and then relax on the cruise on the way back.
We found that most people who do the land cruise include Denali and then the train ride to Mount McKinley. The trains are the ones with the open window cars that give you a panoramic view. Most of the cruise lines have their own train cars. When you board the train, Holland America, Princess, Carnival, etc each have cars attached to the same train.
With Princess, we flew into Anchorage a day early and stayed at a bed and breakfast to make sure there were no flight issues. If you do the land portion first, you send your largest bag onto the boat and then take your smaller luggage on the land tour.
A few months before your cruise, you should go through all of the excursions your cruise line offers and book the ones you want to go on, before they are all booked up. Most tour Denali Park, which is included as part of the land tour. Princess gives you a half day tour, but we upped ours to a full day for a relatively inexpensive price. The Denali Park tour is basically a bus ride into the park where you see it's vastness and animals. The half day tour goes halfway into the park. The cruise lines generally have their own hotel complexes in Denali, but use the same buses for the various cruise lines.
Each port you select will have tours. Anything that is motorized, particularly flights, are expensive. Decide on a budget and book your tours.
We learned that July was the best as stated, and is the most expensive. The key here, is that the salmon don't run until July, which means the animals don't come out until the salmon do.
Cruising Alaska is like cruising a large lake. Spend the money for a balcony room, because the sights, even on cruise days, are beautiful on the inside passage.
Most cruise lines specialize in particular age groups, but not necessarily by choice. People just seem to gravitate to certain cruise lines by age. Carnival Lines are typically for your younger crowds. Princess is more for the 50-60 year old crowd and Holland America runs a little older crowd. I'm sure someone is going to be offended by this, so check it out for yourself.
Just like here, there are cruise line forums. You can log on and see what people are saying about certain cruise lines and land tours. A ball park figure for a 10 day cruise including a land tour is about $10,000.00. Remember, don't skimp on the various tours because you'll typically only do the cruise once and regret not having done what you want.
Lastly, our friend who booked our trip handled all of our transfers and rides between trips. Some people say to book your own tours and save money. We found that the price difference was negligible. Plus, any tour that the ship books that is late or has an issue, the ship will wait or take care of the issue. If it's a tour you booked on your own, you're on your own!