<map lat='53.010238993755976' lng='18.615646362304688' zoom='10' view='0' float='right'/>
North towards Gdańsk
Take the bus towards the Real supermarket. Close to this hypermarket, there is bus stop "Polna" which is a cool place (next to the petrol station). There is a free bus service. You can find the bus stops on the Odrodzenia Street (near theater square). From the city center you can also take bus numbers 12, 14, 28.
In April 2017 this spot gave nothing for UltrasonicNXT for an hour of waiting, but he picked up a lift from the South East (towards Warsaw) spot in just five minutes.
UPDATE October 2018
We (a man and a women) used the "Warszawa spot" with a sign to Gdansk and we just waited 20 minutes. One guy took us straight away to Gdansk
South towards Lodz
All you have to do is just take any bus to Czerniewice for example bus number #11 or #38 (end of the city). When you will see wood it is time to get out :).
South-East towards Warszawa
Take the bus toward Carrefour supermarket. Close to this hypermarket, there is bus stop which is a cool place. There is a free bus service. You can find the bus stops on the Odrodzenia Street (near theater square). But you must be careful! One direction is going to Warszawa and the second is going to Olsztyn!
n0id believes that this warning refers to the split of the roads close to the supermarket. Make sure to be on Szosa Lubicka and you are on the right way to Warsaw.
Another option is to take Tram #1 or #4 in direction of Olimpijska to the final station. This might be easier than taking the free bus, because there are several tram stops close to the center. When you exit you'll see a lot of wood around and a residential area to the north. Cross it and after a few hundred meters you will reach the Szosa Lubicka. Turn right and directly after the traffic light you can find a bus stop which is a good spot to hitch from.
According to the polish site autostopem.net you can also take the busses #22 or #31 to the final station to reach the above mentioned Szosa Lubicka or the Carrefour supermarket.
West towards Bydgoszcz
Take the train number #1 to Merinotex and go to the end of this train.
UPDATE 2015 Tram #1 is not using this route anymore; now to get to the spot you have to go by tram #2 or #5.
South-West towards Poznan
Take bus number #10 or #20 to one of the stations at the Pozńanska street. Take care, because bus #10 turns right after the bus stop Stepowa. Bus #20 goes even further along Gniewkowska street. n0id didn't manage to try it out, so find out yourself which of the bus stops seems most suitable for hitchhiking. Have a look at googlemaps and the public transport website (see below) to know approximately where you should get out.
There is a good website showing you how to get from one point to another by public transport in major Polish cities (in Polish and English).