San Sebastian has the highest ratio of Michelin stars per inhabitant in the world. The whole town seems to be focusing on stars, but as we know, a great restaurant experience is based on much more than just how many stars it has earned. To achieve the best possible experience at any restaurant, the design, atmosphere, history and service are just as important as the taste and presentation. The whole package creates the result and differentiates all the lovely restaurants that you find here. 
In addition to all the star restaurants there are hundreds of Pintxos to choose from in San Sebastian. Pintxos are small bars stacked with bite-sized tapas or small plates. You pick what you please and count the toothpicks or plates when you are satisfied. I think this is the best way to do lunch in San Sebastian, and perhaps Spain in general. This is the way the locals eat, and the Pintxos serve as daily, focal meeting points for them.
San Sebastian is more than just food. Easily put, the town is divided into three parts. Centro has the best shopping. The Parte Vieja is the old town with beautiful buildings and narrow streets, and Gros, with some shopping and several restaurants.
Most of the best restaurants are located outside of the city center, so it is not too importance where you decide to stay in San Sebastian. You will need a taxi anyway. I choose our hotel partly due to location, but mostly based on design, size of the rooms and price. We stayed at the Astoria 7, and liked it very much. The top restaurants we visited were Mugaritz, Arzak and Martín Berasategui, and the best Pintxos was Bar Ganbara. For short trips outside of San Sebastian, visit Hondarribia and do some shopping in St Jean de Luz, which is just across the french boarder.
More info on hotel and restaurants will follow!
