I had posted a few weeks ago about transportation from Venice proper to Marco Polo for a 6:10 a.m. flight and got lots of good suggestions about staying near the airport the might before.

Disregarding that advice , I took the 4 a.m. Alilaguna from St. Mark's Square and was standing in line at the ticket counter by 5:20 a.m. (Granted, I was in the elite line, but would have been OK regardless). I had plenty of time to get the VAT form stamped and mailed and even stroll around a bit before boarding.

This option might be tight, time-wise, in high season, but worked beautifully in December.