Since I knew I would be visiting Terezin while in the Czech Republic, I decided that visiting the Jewish neighborhood would probably help prepare me. It was a wonderful experience.
There were attendants at each synagogue who were very helpful. Guides and audioguides were both available. I recommend starting at Pinkas synagogue. It is so beautiful and the names of the Holocaust victims on the walls will haunt you. Each synagogue and ceremonial hall had impressive museums. Pinkas had artwork by the children of Terezin. It included their photos and some of their personal items.
I really enjoyed the Old-New synagogue. The attendants were very helpful. Since it is a still functioning synagogue, I even met several members. They also had many stories to tell.
Across from the Old-New synagogue is an excellent bookstore. It has great books on Terezin (better than what is actually in Terezin). I strongly recommend taking the time to visit this area.