Dinner in SFO near the Embarcadero
Keep in mind that for all but the most casual, local restaurants, any good restaurant is a "big deal" for reservations on a Saturday night! One Market is quite good, but it is a fine dining restaurant -- not formal, but upscale and a place that requires reservations.
Waterfront Restaurant along the Embarcadero is pretty good, with modern seafood, good views and if you book a day or so prior, easy to get into. I prefer it to any of the Fisherman's Wharf restaurants, but it's still not "the best" in town.
My favorite Italian in North Beach is Ideale... a small Roman restaurant that is best with reservations so you don't have to wait. It's at 1309 Grant Ave., near Vallejo, which is off the tourist path of Columbus Ave.
Even more casual, in SOMA, is Pazzia, on Third Street near Folsom. I don't like the ambiance (I find it physically cold in bad weather, as much of the front area is open), but the food is good, reasonably priced, and the owner is a charmer!
For Cal-Ital in SOMA, I like Lulu. The iron-skillet roasted mussels are very good, and they have oven roasted specials each night. Good portion size, too, for the money. But it is LOUD!! Again, best to book to avoid waiting.
Hope that helps!