North Beach is, unsurprisingly, on the north side of the city, *just* south of Fisherman's Wharf. It's a fairly flat area, and the main roads running through it are Columbus and Union.
There are a lot of great restaurants there. Watch out for the places in Little Italy - a lot of them are pretty mediocre, with some exceptions. Some of the best eateries are:
The House Mo's Grill Mamas (although the queue here is pretty epic)
Those are all pretty special places - if you just need some regular nosh, try Darren's Cafe.
Also in the area is Washington Square, a small open area.
The main buses that serve this area are the 30 and the 8x.