I'll speak to the pintxos since that is what I mostly ate in San Se. It's best to just walk around and head into whatever place looks interesting. Yes it can be boisterous and intimidating, but no one has ever been rude to me for being a tapas tourist. If you speak some Spanish you have a leg up. Most of the food is out on the bar and you just point to what you want (or say "one of those please" since you speak the language!). The bartender often keeps track, but sometimes you need to tell him what you had when you are ready to pay. Sometimes you can grab a seat, but often it is standing room only.
Just strike up a conversation--ask someone what they like. You're in for a great treat so look on it as an adventure.
I'll look to see if I have my list of favorites somewhere, but these things can change even in a place with venerated traditions--so just follow the crowds.
A couple of resources:
http://www.travelcookeat.com/
http://www.todopintxos.com/home/home.php?lang=en

I do have one sit-down restaurant recommendation, right in he old town:
http://www.restauranteurbano.com/en/index.html
Otherwise, I dined on pintxos. A lot of the restaurants that I read recommendations for were definitely cutting edge and expensive, but you will see plenty of menu del dias.

We like Atari very much, also in the old town. Recommend you book ahead via www.lafourchette.com or stop by to book a day or two ahead. It's at 18 calle mayor. They have tapas but also very good meals. It's small but lively with outdoor seating. www.atarigastroteka.com

Another pintxos or tapas bar is on the left as you enter plaza capital from the east. If you walk past the bar, the outdoor seating is just past the bar on the left. Great for people-watching and street entertainment. You can order off the menu or go in the bar, chose what you want and the waiter will bring them out.

For some good information on dining in San Sebastian-Donostia, take a look at Maribel's Guide to the País Vasco (www.maribelsguides.com). Then take a look at: Todo Pintxos (http://www.todopintxos.com/home/home.php?lang=en), which even gives you routes to follow.

The one secret when pintxo hopping is to look for anywhere there's a crowd and join in. Don't be intimidated, you'll always find a place at the bar to order your pintxos. It's also typical to step outside of the smaller pintxos bars with your pintxo and drink, and pay after you've finished.

bookmarking

Have you tried San Sebastián Food? They offer group pintxo tours. And are awesome.
You can definitely make friends while out for pintxos, esp with a little bit of Spanish. And nobody really cares what you're drinking....if she feels uncomfortable with water, order a 'mosto' or grape juice. V. common.
As far as a short list I agree with YORKSHIRE's resource recommendations

Just relax, a glass of water is perfectly fine an the whole idea of going for pintxos is very laid-back and very social.

Plenty of options as you say, but if you want to sit down outside, these are two great choices in the Parte vieja/Old town.
Gourmet pintxos (not too fancy) at Cuchara de San Telmo: http://www.tripadvisor.com/Restaurant_Review-g187457-d877927-Reviews-La_Cuchara_de_San_Telmo-San_Sebastian_Donostia_Guipuzcoa_Province_Basque_Country.html
Astelehena right on the main plaza: http://www.todopintxos.com/bares/bares.php?id_bar=121&do=vista_bar

It's a good advice not to make too many plans in advance, but you shouldn't miss some of the house specialities that are directly prepeared in the kitchen and not on display in the bar. The waiters are usually very helpful and patient, don't be afraid to take up their time and ask in whatever language.

Don't miss:
Brocheta de gambas (prawn skewers) at Goiz-Argi: http://www.todopintxos.com/pintxos/pintxos.php?do=verficha&id=39
La Hoguera (the bonfire) at Zeruko: http://www.todopintxos.com/pintxos/pintxos.php?do=verficha&id=86
Txistorra in Ganbara: http://www.todopintxos.com/pintxos/pintxos.php?do=verficha&id=42
Braised veal cheeks on red wine in Borda Berri: http://www.todopintxos.com/pintxos/pintxos.php?do=verficha&id=157

My last visit was about 6 years ago, but these sit-down places, that I enjoyed, are still going strong. Moderate prices:


http://www.restaurantelarampa.com/ubicacion.html ( seafood, with outdoor dining option)


http://www.juanitokojua.com/en/index.html (traditional Basque; rustic and charming)

Someone mentioned San Sebastian Food, here is the link...it was also recommended to me for my upcoming trip in the summer.
http://www.sansebastianfood.com/en/about-us.php

I too love Todopintxos as a primer to educate myself of what is being served...and to get the mouth salivating!!!

this may also be of help

http://www.blogseitb.us/basquetourism/2010/11/20/a-pintxo-is-not-a-tapa-and-a-tapa-is-not-a-racion/

When you go for Pintxos you often just grab a plate of anything cold. You save the toothpicks so the bartender knows at the end how much to charge you. It can't hurt to point out what you want if you're not sure if you should just grab it. I once tried to grab a plate and the bartender stopped me because there are some things they want to throw on the grill quickly to heat up. Don't worry about planning too much. Definitely download maribelsguides for a list of the classic places. Try the wild mushroom plate at La Cepa if you like mushrooms. When ordering food a racion is a large plate, a media racion is a half size portion and a pintxo is a bite or two with a toothpick in it.

"a pintxo is a bite or two with a toothpick in it"

Not quite what I would describe as a pintxo in Donostia or anywhere else in the Basque country or Navarra today.

I love the toothpicks myth

bye, Cova

Yes, (many years ago) we used to pile them up on the bar and they would inadvertently get knocked off, ending up with a few hundred others lying on the sawdust covered floors, but happily things have improved somewhat since then.

A little more about pintxos and toothpics:

Most cold pintxos on display in the bar would have a toothpick-like skewer through it or the entire pintxo is presented as a skewer (as for example the perhaps most famous pintxo in town, the classical Gilda named after Rita Hayworths character in the movie of the same name, or the great prawn-skewer at Goiz-Argi).

Most places don't count the tooth-picks though, but there are some bars catering to lots of tourists that do. I almost turned red with anger when a new barman at one of my casual hangouts from the 1990's, Aralar, tried to instruct me of the "system" a couple of years ago: You are given large plates and urged to pick several pintxos with colourful skewers that you present to the barman at the end. The battered merluza pintxo with a pinch of lemon here nevertheless is divine, and I can't keep coming back here all the time at least for a bite of this and a glass. Usually fine atmosphere in here and some tables in the back to sit down and relax and perhaps have some raciones too and make it a full meal. http://www.bararalar.com/

Some of us haven't eaten any of the old style "traditional" cold pintxos in a very long time, but I guess Aralar a good place for tourist to hang out.

Gildas are overly popular in the Basque Country...a touch of sin in your mouth, as the movie...

Just found out that the Gilda history starts in Casa Vallés in San Sebastián, an institution in town where food and atmosphere is great, rustic, and laid-back, a far cry from the gourmet hype (and with lots of toothpicks pintxos and delicious bocadillos). I recommend it very much. It's in the Reyes Católicos street just behind the cathedral. Long tables inside can seat some 50 persons, and also an outside terrace: http://www.barvalles.com/portada.html

The Gilda history started in 1946 when the place of the Vallés brothers from Olite got license as a taberna. The then new house invention olive, anchovies and green, hot pepper on a toothpick was named after the Gilda movie which premiered the same year.
http://historiasdelagastronomia.blogspot.com/2008/05/la-gilda-pintxo-y-no-rita-hayworth-naci.html

As an American I stay out of the family fight reagrding the differences between tapas, pintxos, and raciónes. As noted on a similair topic I just eat them and watch others debate how many patatas bravas fit on the head of a palillo.

In case someone is looking for gildas in Madrid, they serve them at the Victor Montes in the Mercado de San Antón.


Bye

Robert:

What do you think of the two restaurants I mentioned? Still good enough to keep on my list, or to recommend?

La Rampa is always busy, we were there last summer in July following the fiesta in Pamplona. It's basic, but the prices are still attractive and the seafood very fresh.

I haven't been to Kouja lately, but I wouldn't exclude it from your list of places to try for more traditional dishes, nothing fancy. But like a lot places in the Parte Vieja, wine prices have gone up somewhat because of the number tourist flocking to the area.

A glass of wine in the Parte Vieja will cost €1 to €1.50 more than what we typically pay for the same glass of wine in Pamplona. And forget the price of a pintxo. It's almost as bad as going out for tapas in Old Madrid.