I'm due to land in warsaw on the 17th of October. I will be starting off in Poland and working my way to Serbia via Romania and Bulgaria! If anyone is planning to be around those areas or will be in Poland at this time please hit me up! I'm absolutely crapping myself! Thanks!
I've found all of those easy travelling, and plenty of travellers around at least in summer.
Look out for free walking tours in the main cities - also a good way to meet a crowd of people.
Agree with the above - there are free walking tours in a lot of cities which can be a great way to meet people, and get the layout of the city. Plus interesting information on the city! I've also found likealocal websites and Use-it Europe maps great as they aren't purely based on tourist locations. Oki Doki hostel & there is a museum that I can't recall the name of off the top of my head in Warsaw that are really good. (and i rarely do museums!) Plan a couple days in Krakòw if you have the time - it has a lot to offer.