If I have tickets to go to the top of the Campanile- is there a way to avoid the long waiting lines? I know we can 'book' a time online to enter St Marco's Basilica.
Get there before it opens. I think it was 9am when I was there but that was winter. Summer could be earlier. A half hour or so later there seems to be a constant line and it gets pretty crowded at the top.
For a less crowded native and an exceptional view across the Laguna to the east, as well as a magnificent view of Venice , take the 5 minute vaporetto ride to San Giorgio Maggiore . The bell tower there is less-known and less likely to be overrun by the day trippers that amass in P.za. San Marco.
Great suggestion to go to the SGM tower. AND you can get some awesome photos looking back at the basilica and the belltower you didn't climb.