This is one of the more annoying achievements. There are 159 posters all over the city and one of them, poster 63, is a massive pain. But the rest are just run to and snag. In the video below, he listed each poster in the comments with a time stamp so you can get what you need, or just do them from the start. I personally waited until Chapter 15 to begin these as that means they will all be ready and nothing blocking any of them. Here are two options to help you attain this achievement:
Option 1 - Interactive map - http://maps.achievementhunter.com/ (Just click on Mafia 2, when I tried to copy the exact link it gives it just failed to load)
Option 2 - Video going in linear order as opposed to numerical order - I did not make either of those guides so please give credit to the ones who deserve it. Any who, let me know if I can help more!