I used a stud finder successfully to mount my TV using lag screws. Others on here have posted that they find 2 studs, mount some wood between them, and then mount a TV to that. But you didn't state what you are mounting - so, depending on how heavy, if a hook can do the job, try those 3M Hooks that you can put up and remove without damaging the wall surface. I use these in the bathroom for towels and by the door for coats in the winter. Stating what you are trying to mount would help out a lot though...