Been doing this for years. I use a hammer with the face of the hammer flat to the wall, lightly tapping on the wall until I find a solid section of drywall, you'll feel and "hear" the difference when yo find the stud. Once the stud is found, I transfer the found solid section down to masking tape on the floor, then go 16 or 24 inches (depending on the stud layout) on center from that point on, transferring the marks up the wall with a level off of the masking tape. If you are working with an unfinished floor skip the masking tape and mark the sub-flooring.Measure your studs in wall before you cover it. Rite it on paper ,(save paper ) measure right to left or left to right but remember which way you tape measured it ,plywood can get pricey ,and there's stud finders .