<map lat='43.311939092640564' lng='-1.9820022583007812' zoom='13' view='0' float='right'/> Donostia (Spanish: San Sebastian) is a city in the Basque Country, in the north of Spain near the French border.
1) Try the petrol station closest to the city centre at Av de Navarra/Calle de Zemoriya. Hitchhikers have found French cars here.
2) Take local transport (bus or train) to Irun and walk towards the border. After crossing the bridge into France take the highway right along the river, to the péage. It's easy to go to Bordeaux. Stand just after the péage because drivers will be less concerned and quicker to pick you up after crossing the border.
3) I think the best place to hitch hike out north is at the roundabout by the end of De Zorroaga Ibilbidea street entering GI-20. There is no perfect place for the cars to stop, but they can manage if they want to. I would say the best is to stand at the crossing with a sign Irun, because after it the ones entering the GI-20 keep to the left. I got a ride there in 20 mins. Nykstukas9
There are several motor way entrances in San Sebastian to go south towards, Vittoria/Madrid or West toward Bilbao in which you can stand in front the entrances with a sign to grab a lift. You can also try the petrol station in the centre at Av de Navarra/Calle de Zemoriya.
The western most entry point to the highway/motorway system of roads is at De Tolsa Hiribidea where there is a great place to stop and talk to people at the traffic lights before they get on to the motorway. You can walk, take many buses the centre to there, just ask if the bus is going to the Universidad or take the metro to Lutgariz station and go left once you exit the station.
To travel towards Vitoria, Burgos or further south to Madrid, you want to get a ride to a service station on the N1. This is the main highway, from north of Spain to Madrid and the principle road Spanish people take, because it is not tolled. Stand at any of the motor way entrances with a sign saying N1 and possibly sur (south) and you should get on the N1 easily enough. As this is a national road and not a motorway there are plenty of service-stations along the way. Meaning you only need to get short ride first and you will be able to change for something longer.
West towards Bilbao
You want to get on the AP-8, a toll motor way that goes west along the Basque coastline. There is a service station shorty after you get on the motorway, but its is small and quiet. The next service stop on the motorway isn't until, Deba so aim to get at least here. Most people coming out from Donostia-San Sebastian will probably only be going to the other little towns nearby.
A good spot to do this is at the roundabout called 'Plaza de Pio XII'. There's one exit on the roundabout that goes in the direction of Bilbao A8. Just before the entrance to the highway the cars have to stop at a traffic light, this is a good place to talk to people and try to get a ride.