And here is a link to "Rick Steves' Europe: Graffiti Wall" which contains user-submitted tips on a wide variety of topics.
As with all links from this blog, please remember that a link here to one page does not imply an endorsement of every and any place THAT page might link you to. The web is big. And diverse. So any inadvertent detours to places or topics that aren't very pilgrimage-y are just that- unintended!