Standard operating procedure in a pinxto bar is relatively simple. Figure out the specialty of the house and order it. Usually this is a hot pinxto versus a cold pinxto that you will find on the counter. Order a drink - Txakoli is a great choice for a white wine as it goes with almost anything. Plus, it is cheap and delicious. Should you need a red wine, ask for a Rioja Crianza. Have a few bites but not too many as there are many more places to explore. Throw your napkin on the floor instead of putting it on the counter.
The following are the best San Sebastián pinxtos bars per my taste:
Bar Nestor - the specialty of the house is grilled steak. Other stand outs are the grilled peppers, tomato salad and Basque cheeses.
Ganbara - the specialty of the house is grilled mushrooms and the signature dish below was just mind blowing. In addition, all of the hot tapas are superb.