Suwałki is a city in northeast Poland along the E67 "Via Baltica" highway. It is a major transit point between the Baltic countries and Poland and the last major settlement before the Lithuanian border.
North towards Lithuania
From the PKS bus station, walk north about 1km along Utrata street (highway 8 (E67)) till the roundabout. The highway 8 turns right here on Gen. Kazimierza Pułaskiego, so take the right turn and continue straight for 2kms until you are almost out of town. You can hitch at the junction of Knuta Olafa Falka street (opposite the Oil Transfer petrol station). There is a hard shoulder here just wide enough for cars but not trucks; however, traffic is moving reasonably slowly to make it a good enough place to hitch.
If you are arriving from Augustów and you are dropped off at the beginning of town where the bypass road splits off, there is a large lay-by just past the roundabout where you can hitch and where cars can pull over. (Drumroots even had a truck just about squeeze into the lay-by to give him a lift).
The road enters Lithuania at the Budzisko-Kalvarija border crossing (about 25kms from Suwałki) where long-distance rides further into the Baltic countries are possible.
From the PKS bus station, walk south on highway 8 (E67) along Utrata street for about 4.3kms until you reach the roundabout at the southern edge of town. Hitch on the highway about 60m after the exit from the roundabout. Otherwise, there is a large Orlens petrol station at the roundabout if you want to ask drivers (or if you get caught in the rain/ at night).