I have very close friends who live in Mestre, just a drive over the causeway..so I have been to Venice at least ten times. My advice is simply to walk and absorb the unique ambiance. You can't get lost for long as the yellow signs on some buildings will point you in the direction of some recognizable landmarks eg Piazza di Marco, Accademia, Ferrovia etc. Get a list of must see sights on the internet (www.fodors.com for instance) Venice is a city for walking and riding the vaporreto( the aquatic buses) on the main canals. It is a city to be experienced as it is my second favorite city topped only by Sydney. Avoid the touristy restaurants and eat where the locals eat in the side streets. Enjoy the city. You are in for a rare treat. March is a good time; you may still see it in the fog and mist. Ciao !