One of the things we've discovered about the house we are living in is that the walls are made out of plaster. It looks exactly like dry wall, but don't let it fool you. It is a different breed of wall.
1.We nailed into the wall and the wall cracked. Solution: We have started putting tape on the walls first and then nailing into the spot with the tape. This minimizes cracking.
2. The nails will just not go into the wall! Solution: Move the nail over an inch or so and just hit it a lot harder.
3. Sometimes the plaster is so hard that the nail bends instead of going into the wall. Solution: Throw the nail away and use a bigger one.
As you can see, we have no idea how to deal with plaster walls. We're working on it though...and learning new things every day!