You may be able to find the studs without a stud finder if you don't want to buy one - (also - does anyone know how well a stud finder works if you have metal/mesh lathe?)
Most of the time, an electrical box is mounted to a stud. So you can guess that the stud is either to the left or the right of an outlet or switch.
If you have forced-air heating, and the vents are in the walls (as opposed to the floor), the vents are situated between two studs. (sometimes they're a full 14.5 inches across - sometimes they're smaller. If they're smaller, take the register cover off and poke around with a hanger to find the studs.)
You may also be able to see where other molding was nailed (baseboards, crown) - most likely, they were nailed into studs.
And as a last resort, you can cut across the wall with a reciprocating saw until it meets some resistance. There's your stud.