I grabbed a plain magnet from the refrigerator, and tied a piece of dental floss to it -- any fine string or thread would work. Dangling the magnet along a wall revealed all the nails and screws in or beneath the drywall. Once I marked a few with a pencil, it was obvious where the studs were.
I've read that people find this method too slow, but the electronic stud finder always leaves me guessing. Once I saw the pattern of fasteners there was no question I had found studs. If you want to speed the process up, a strong and light rare-earth magnet would really seek out the nails.