Recommend hotel or BB? For the included cities

Lucerne: Hotel Wilden Mann; nice people, good rooms, good restaurant. Close to (or in) the historic center. Reasonable walk to railway station

Salzburg: Altstadthotel Weisse Taube
Vienna: Pension Suzanne

Dear God, Heidelberg of course! Mannheim has grown on me, but I can't really recommend going out of your to visit, much less stay there. The only place I've spend the night in Heidelberg was the Hotel Hollander Hof. Right by the old bridge, you can't beat the view if your room faces the river.

Ditto what Tom said - about Heidelberg, the Hollander Hof, AND Mannheim .

The first place I would try is the town's own website at www.town.de (or .at or .be). I tried this in Cochem in 2008, but there was a winefest in Cochem and no one wanted to rent a single room, so I stayed here in Treis-Karden, 7-10 min from Cochem. Similarly, for Salzburg, I stay across the river in Freilassing, Germany, about an 8 min train ride from the Salzburg Hbf at Hotel Rupertus, not a B&B, but economical.

Lucerne-Hotel des Alpes. Just an awesome view from their balcony rooms.
Salzburg--Star Inn Zentrum. Cheap chain hotel. Awesome location. 10 min walk through the tunnel to old town.

Thanks for all the comments so far.

Agree with Michael about Hotel Weisse Taube. We stayed there, too. Great location, friendly staff, nice continental breakfast (with eggs!: Please pass this idea on to the French). Other recommendation would be Goldenen Ente. Didn't stay there, but kept ending up in their downstairs restaurant for dinner.

Hotel des Alpes in Luzern, Weise Taube in Saltzburg, and Best Western Kaiserhof in Vienna.

Although it is a bit out of town, buses easily take you directly to old town of Salzburg from Hotel Zur Post, a nice three star hotel. They rent bikes and have a good breakfast and free computer use.

Although it is a bit out of town, buses easily take you directly to old town of Salzburg from Hotel Zur Post, a nice three star hotel. They rent bikes and have a good breakfast and free computer use.

In Ghent - check out the Marriott. I know it sounds nuts to go to Europe and stay at a Marriott and not a fun, local hotel. But the Marriott is in an old building right on the prettiest canal. You can get a room with a canal view.