I cannot find any guidance online for purchasing advance tickets to museums and other popular sites in Bruges. Can it be done, and if so, how? Otherwise, how can I avoid long lines at ticket windows?
I've been to Bruges several times and never come across long lines for anything. Purchasing a city pass at the TI office could help a bit.
Agree above, even if it was possible, you don't need to buy anything in advanced for Brugge.
The only thing Rick suggests that you would book ahead would be a private, guided tour.
Even as busy as Bruges can be I have never seen lines for anywhere. The only time we got tickets in advance was for seats in the stands for the Procession of the Holy Blood. Other than that, no.
I agree, never saw a line of more than three people.