Food and beer:
Go to the market on 't Zand on Saturday morning, they do great food.
Treat yourself to a 'wafel met slagroom' (this means waffle with whipped cream) in a cafe.
The brewery is a good tour, but you can just go to the bar for a drink. It gets very busy in the afternoons and can shut early.
Don't just try white beers! Try Leffe Brune (looks serious but isn't), Kwak (just for the glass) or De Garre (only available in a little bar down a side street between the Markt and the Burg, apparently they can legally only serve you two!)
Picking chocolates one by one can get expensive, and its hard to tell the difference between the expensive and cheaper shops.
If you are buying chocolate for lots of people, head to a supermarket for cheaper boxes of brands you'll recognize. Supermarkets are on Oude Burg, Langestraat or Noordzandstraat.
Also try the smaller waffle biscuits with caramelised brown sugar in the middle or 'Speculoos' biscuits.
Go to the Central resturant in the main square and have the Flemish Beef Stew. It is to die for.
Getting your bearings:
From the Markt, walk the main shopping loop. With the belfry to your back, take the street to your left, Steenstraat, which turns into Zuidzandstraat and ends at the large square called 't Zand. Turn right and right again up Noordzandstraat, which turns into Gelmundstraat, bear right to get back to the Markt. (around 30 mins walking shopping!)
Normally a quieter walk. From the Burg, walk down Hoogstraat, continue on into Langestraat and keep going to Kruisport, one of the old city gates. To the left, there are a couple of windmills if you wander along the side of the canal. Head back along Langestraat or consult your map and pick your way through the small streets. (around 30 mins walk looking at the windmills)
Eat at Cambrinus, or get a few frites from one of the stalls in front of the Belfort.
Go to the Halle and Belfort, The Groeninge Museum and the Begijnhof. Drink at the Garre and Brugs Beertje definitely. Kelk and Vlissinghe are good too.