Winter has to be one of the best times for visiting Venice. Post Holiday season excess means a quiet January for most, however their loss is your gain. The heaving crowds ease up and you can explore the city, get lost in narrow alleyways, wander into boutiques and eat in half empty osteria's almost forgetting you are in an era of mass tourism. Winter brings a certain misty aura which gives the city a certain romance. Crisp mornings are perfect for an espresso and pastry to fuel you up for a day of random exploring. Gondola rides are expensive but still de rigueur. Try not to plan too much and just go with the flow.