One of the first restaurants we remember going to as a kid was Schroeder's, the century-old German joint on Front Street. The stags' heads and beer steins were certainly noteworthy, but what impressed us most was our waiter, a brisk, tuxedo-clad pro with a perpetually raised left eyebrow and a mordant sense of humor. Later in life we realized that the waitstaffs at all of San Francisco's old-time Financial District restaurants -- Tadich's, John's Grill, et al. -- are entirely built upon that Schroeder's prototype. Especially that at Sam's, a longtime bastion of the three-martini lunch and the simply grilled sand dab. The waiters there will not introduce themselves by name; they will not brandish yardstick-long pepper grinders. But they will steer you away from the questionable entrees, bring you food and drink with alacrity, drop the occasional deadpan observation, and in general inspire you to put your stomach (so to speak) in their hands. Tip big: These low-key professionals are of a dwindling breed.