Haskovo is a city in South-Eastern Bulgaria.
Towards Svilengrad, Turkey, Greece
It is relatively easy to go out of Haskovo in direction to Svilengrad that later on leads to Turkey or Greece. To do that take the trolley bus (there is only one, so there can't be much confusion) in direction to ZMM (zeemeemee). The price of the ticket in 2012 was 0.80 BGN. Get off at the last stop and walk few hundred meters until the roundabout. Follow the road direction to Harmanli and Svilengrad. There is a good spot to HH, usually you can find a lift within 10 minutes.
In order to get to Plovdiv, Sofia or further west you should take the bus that goes to Dimitrovgrad. You can take it from Lebeda, Chochko or Rakovska. The price of the bus in 2012 was 1 BGN. Tell the driver to stop on the junction that leads to Plovdiv. Then walk to the bridge that is above and you can start hitching from there. It is relatively easy because the cars have plenty of space to pull over. The rumor is that in the middle of next year (2013) the highway that connects Sofia with Istanbul will be finished and it will pass very close to Dimitrovgrad.
Towards Stara Zagora, Burgas, Varna, Russe, Romania
Do the same as if you would go to Sofia but when you get off at the beer factory Astika don't go on the bridge and keep hitchhiking north. The ring of Dimitrovgrad is new and there is a lot of traffic passing by.
There are several parks within Haskovo that are suitable for urban camping. You can camp on the Kenana park-forest located in the north-western part of the town or on Yamacha located just behind the monument of the Virgin Mary.