Belle,

look i.e. for "Rösti", the Swiss type of hash browns. Assuming you're not a Vegetarian you should also try a "Bratwurst", a sausage. One of the best places for it is the "Vorderer Sternen" at Bellevue square. You can have it as take-away or eat inside.
Another good thing is ice cream, there is a brand called "Mövenpick" which has really good stuff. You find it at Bahnhofstrasse and several other locations. (Btw: it's also served on Swissair flights.) As for the best chocolate in town, I'd suggest "Teuscher" at Bahnhofstrasse (also at the airport) offering unique champagne truffles.