For the sake of answering some queries raised along the way to writing this column and offering a bit of general advice, below I'll break down what I consider when reviewing a wine bar.
Obvious and primary, a wine bar should have an exciting selection of wines that thrill and most to all should be available by the glass. No respectable wine bar offers only a tiny fraction of wines by the glass and expects any other wines to be bought by the bottle. As this is California, many bars hinge their selections on in-state labels as much because winery reps are always at the door or on the phone as because their clientele will expect it. California drinkers are used to big styles so other common regions are Argentina, Australia and Spain. Personally, I like being surprised by unusual domains, but I've been guilty of cleaving to comfort wines so I won't cast aspersions.
Typically, a wine bar offers light cheeses and breads or crackers to pair with a drink. Rare is the bar that offers more - different fruits or nuts or even sweets or dried meats. The cost is obviously a factor as are food preparation and hygiene codes. Many wine bars are part of a restaurant and of those only a few would ask your party to relocate from the bar to a table if you decide you'd like to sample the chef's fare.
It's vogue for many a popular bar to keep a very low-lit ambiance, along with rather loud music. I find it unfortunate since I don't care to strain my eyes over a menu or strain to hear my company. But I'm outvoted here. Dark & loud seems to infer a classy environment. The music varies some but generally you can take from the style playing the sort of clientele the bar expects - jazz standards (Frank Sinatra, Ella Fitzgerald) tends to imply older, well heeled customers, pop jazz/rock (Us3, Matchbox 20) is standard for middle aged yuppies and more than a few hipsters, hard rock (Metallica, Led Zeppelin) invites the scruffy and hard of hearing from all ages.
As with any bar or restaurant service should be prompt and thorough. Beyond that I appreciate kind servers who won't talk down to me. Seems self-explanatory, really.
A good wine bar will anticipate a variety of sizes in parties, from comfortable bar seats for the solo drinker to overstuffed couches or convenient benches & tables for large parties. Keep in mind, a party of 6 is a robust challenge to the usual wine bar and parties over 8 will often strain resources. At a certain point large parties should make a point of reserving rooms if an evening at a wine bar is desired, rather than a pleasant watering hole before dinner or other entertainment.