Szczecin is a city in north-western Poland with more than 420 thousand inhabitants (7th largest city in Poland).
By motorway A6 > autobahn 11 (E28), from petrol station
From bus stop Plac Zwycięstwa which is close to Brama Portowa, or from ul. Wyszynskiego at the Oder river, take bus 81 (only those ones with letter 'b' on the timetable) and go to Kołbaskowo. Beware, these buses are rare. Another option is getting a bus from central bus station in Szczecin (about 10 buses a day, beside Sundays). In Kołbaskowo (the last stop), walk back 200m to the bridge above the highway. Walk down to the highway, then walk for 15 minutes in the direction of the border. Soon you will see 2 petrol stations where you can ask drivers for a ride. The petrol stations are situated roughly 2km from the border itself and since there are no more junctions any more, all cars are bound for Germany.
North and northeast towards Świnoujście and Koszalin, Gdańsk
By expressway S3 (E65) / national road 6 (E28), from slip road
From city centre e.g. from Brama Portowa take tram 7 or 8 and get off at the last stop called Basen Górniczy. From there take bus 79 or 73(Z) and get off at Zwierzyniecka. Ask people or driver where to get off as buses don't stop on every stop until you press the stop button. Saying "autostop autostrada" should be enough. Next stop is 3km further away! From bus stop Zwierzyniecka go straight uphill for about 500m till you get to the junction with motorway A6 / expressway S3 and national road 10. Cross the motorway on the bridge and turn right to slip road where you can find little lay-by. Make a sign.
South and southeast towards Gorzów Wielkopolski, Zielona Góra, Wrocław and Poznań
By expressway S3 (E65), from bus stop or sliproad
This spot is just before the place for hitching in the direction of Koszalin, so check it for more details. Once you get to Zwierzyniecka bus stop you can hitch from there or walk up 500m till the motorway entrance. Go behind the turn, because cars are very slow there and there's plenty of space to stop. Make a sign.
East towards Stargard Szczeciński, Bydgoszcz, Warszawa
By national road 10, from bus stop
This spot is located very close to the spot in the direction Warszawa. In this case if you take bus 79 get off at bus stop Balińskiego nż, which is the first one behind motorway, next to Lotos petrol station. Walk straight to the crossroad and behind it turn left, go for about 300m to the bus stop Unikon. This is the spot. If you take bus 73(Z) you can get off exactly at the bus stop Unikon.