I highly recommend a good map, even for 24 hours on the island. I can walk around Madrid, Barcelona, Athens, and Nice without a map. Not Venice! It is the only place I always bring along a map.
An adable restaurant in VCE is Casin Dei Nobili. Open for dinner beginning at 7:30pm. Get there no later than 8pm, or you will not likely get a table. The location is on the route from the bus station (Piazza Roma) to the Accademia bridge. It is about 5 minutes from the bridge, before the restaurant Taverna San Trovaso (which is touristy, but OK).
Tel: +39 041 241 1841
Address: Calle del Casin, Dorsoduro 2765
Notes: Closed Monday
For lunch, I like a difficult-to-find place near San Marcos called Cava Tappi. They have outstanding wine by the glass, and fantastic classic Italian lunches. Location is Campo della Guerra, 525/526. Tel: 041-2960252
Out the door to the left a short distance is a great Gellateria.