The advice you have been given is good. I have cruised Alaska 8 times with Princess and it is true when you get into glacial areas the ship will stop and turn so that both sides of the ship get good viewing. Most of the cruise will also be in the inside passage so there will be ilands or land on both sides of the ship.
The one great thing about cruising Alaska is that it is never the same due to the fact the glaciers change shape and you never know when or where you will see wildlife. In other words don't just look for the glaciers you should also keep your eyes open for the sealife that can be on all sides of the ship at anytime. I have spent hours watching dolphins and porpoise from the deck of a ship as well as spotting whales.