Skagway:
it’s a small town to walk through, if it’s your first time. Definitely book the White Pass Railway to ride.
Juneau:
It’s very easy to do whatever you wanna do here, MUCH cheaper than the cruise line sells. When you get off the ship, at the base of the Mt. Roberts Tramway; they have little booths setup with all kinds of tours (bus to Mendenhall Glacier, whale watching, etc) all very reasonable prices ran by locals. Also if you want to try King Crab, Tracy’s crab shack is right there too.
Ketchikan:
Usually this port stop is so damn short; we either just walk the little creek Street, or go to the LumberJack show.