You need a template so you know where to drill the holes for the cord, mounting plate and the mounting screws. Also you will need an extra persons to help hold the unit up while you screw the unit in from the top. An electrical outlet is also needed to plug the unit in.
You are going to want to make sure you have a stud right behind the wall that you are going to mount the microwave. If you have cubboards above the microwave it will work even better because you can support it from both sides.