NOTE: This is an example of installing a medicine cabinet with a 2" or more lip.

Preparation
Using a stud finder, locate two studs far enough apart that a cabinet will fit into. Our cabinet is 13 ¼" wide (do not measure of overhanging  lip, just the part this is going to be inserted into the wall.) Find a space on the wall that you want to install the cabinet that is at least the width of your cabinet.

Materials

• Stud finder
• Keyhole saw
• Tape measure
• Hammer
• Drill
• Level
• Nails and wood screws

Step-by-Step

1. After you have located the studs, punch a small hole in the wall with a keyhole saw to take a look at what is behind it. You are looking for wires that might be in the way.   If there are no obstructions, cut the hole big enough to insert your hand to feel around.
2. Cut the drywall over to one of the studs and find the edge.
3. With a piece of cardboard, make a template of the medicine cabinet. You are going to use this as a guide to cut the whole in the drywall.
4. Place the template on the wall and mark where you are going to cut. Check it with a level before you draw the lines.
5. Cut out the marked area with the keyhole saw.
6. TIP: If one of the studs is a bit further that the width of the cabinet, cut a spare piece of stud (a 2"x4") and nail it into the exist stud. You are looking for a snug fit when you insert the cabinet into the wall.
7. Place the cabinet into the opening and check if it's level. Make any adjustments now if you need to.
8. The cabinet should be marked where the screws are to go. Using a drill, insert the screws in at an angle into the stud. (You want to make sure that you miss the wallboard with the screw and hit the stud, which will support a lot more weight.)
9. Set the level on it one more time.
10. After the screws are in, add the shelves.
11. Now you can save some serious counter space!