After moving into a "new" home you might realize that the walls are made of plaster and not drywall. If you try to hammer in a nail to hang a picture, the nail might actually bend in half. Even so, it is possible hang numerous pictures throughout the house.
Put a piece of masking tape over the spot where you plan to put a nail. This will help to give your plaster some extra support so it does not flake off around the nail hole.
If you are hanging small pictures on the wall the easiest way to accomplish the task is to use small nails. Don't try to hammer the nail straight into the wall. Instead hammer the nail at a 45 degree angle for best results.
For bigger pictures try using a power drill to create a pilot hole for your nail. Screws also make good alternatives to nails and put less stress on the plaster.
If what you are hanging is not very heavy you might be able to avoid putting any holes in your wall all together. Check out adhesive hangers as an alternative to nails and screws.