Hanging wall storage cabinets is not the same as hanging a picture. Due to the weight of the cabinet and its contents, it must be mounted directly on wall joists. The cabinet must be level, and it must also be plumb (straight up and down) along the sides and the front. In older houses, it is not uncommon for the walls to be leaning forward.
Measure the back of the first wall cabinet, along the height and width. Mark the dimensions of the wall with a pen, angle hook and level, so the horizontal lines are level. Find and mark each stud within the perimeter outlined area, using your electronic finder. Mark the positions of the studs on the back of the cabinet, measure the distance of each pin from the vertical lines on the wall. Mark vertical lines on the back of the cabinet at the same distance from the edges.
Drill two guide holes on the back of the storage cabinet at the top and bottom of each vertical pin line, one-half foot from the top and bottom of each row. Set your level beside the front of the cabinet. Use your screwdriver to loosen the screws if necessary and stick shims behind to move the cabinet forward or backward and get it soldered. If the top of the cabinet is tilted forward, loosen the lower screws and shims behind the bottom. If the bottom of the cabinet is tilted back, loosen the best screws and shims behind the top. Tighten all screws.