Anytime you are hanging a picture up on a wall, you should first find a stud in the wall to make it more secure. A quick and easy way to find a stud is with a stud finder, but they can be unreliable from time to time. The best way to find a stud in a wall is to measure 16" from the corner of the wall you are trying to find the stud on. Follow up with a stud finder to confirm before drilling a hole or making a nail hole. This will give you a really good chance to find the stud.