You can use any of several simple methods to discover the locations of structural members.
The locations of studs and joists hidden by walls and ceilings can be determined in any of several easy ways.
Since most homes are built with these structural members spaced 16 or 24 inches apart, from center to center, simply pick a corner, measure out in increments, and then tap the surface. If you hear a hollow sound, you are between a stud or joist; if you hear a solid sound, you have hit your mark.
Another way—which is foolproof—is to use a stud finder. This inexpensive electronic device beeps or flashes when it passes over a stud or joist. You simply slide it along the surface until it finds a solid framing member. Simply measure out 16 or 24 inches and then slide the device over the area. Stud finders are readily available online.
You can also find studs or joists by looking for small dents created by the heads of the nails that attach the wallboard to the supporting members. You can make them more easily visible by shining a bright flashlight at a steep angle to the wall.
If your house has plaster walls and ceilings, you can find the studs and joists by either measuring out from a corner 16 or 24 inches and driving a small nail in an inconspicuous area, or you can use a stud finder.