These methods rely on detecting fasteners used to attach drywall or using standard construction spacing and component placement as clues.

Magnet Method: Use a strong rare-earth magnet (neodymium). Tie it to a string or wrap it in a thin cloth. Slowly slide the magnet horizontally across the wall. It will be attracted to the metal screws or nails used to fasten the drywall to the studs. Mark these spots vertically; the stud runs along this line.
Knock Test: Gently knock on the wall with your knuckle. Move horizontally across the wall. Areas between studs will produce a hollow sound. When you knock over a stud, the sound will become more solid and dull. Standard stud spacing is usually 16 inches (sometimes 24 inches) on center, so once you find one, measure horizontally to estimate the next.
Outlet/Switch Clues: Electrical boxes for outlets and switches are typically attached to the side of a stud. Look near an outlet/switch and probe gently with a thin nail or drill bit just beside the box to confirm the stud's edge. Then measure 16 or 24 inches horizontally to find adjacent studs.
Baseboard Clues: Look closely at the baseboard trim; you might see small dimples or filled nail holes where it was nailed into the studs.

N/A - Offers several non-electronic ways to deduce stud locations using basic physics and knowledge of construction practices.

Use Magnet, Knock Test, or Outlet Location