There can be a number of reasons why one might need to remove the radio/stereo from a Ford Focus, although the most common reason is to replace it with an aftermarket stereo. The radio mount can vary depending on the year of the car, so the removal process can also differ. Also, many Ford models have antitheft systems in place that you will have to deal with.
Disconnect the car's negative battery cable.
Detach the button panel bezel if the radio unit comes with it by pressing the button near the top left corner of the bezel to release it.
Look for the four special holes on the radio unit; there are two on each edge of the unit. These radio units with the holes are on many models made prior to 2005.
Insert U-shaped Ford radio removal tools, available at any auto stereo store, into the holes; you'll have one tool on each side. Insert them all the way in, then lightly push them outwards as you remove the radio unit, pulling the unit squarely out of its opening.
Take off the trim panel bezel surrounding the radio unit if it has one instead of the mounting holes; this usually involves using a trim stick to detach the clips. Remove the mounting screws behind the bezel with a screwdriver or Torx bit and pull out the unit.
Disconnect the electrical connector for the power supply from the back of the unit, along with the antenna lead and the speaker wires. If one is equipped, detach and remove the plastic support bracket that is on the back of the radio unit.
An auto supply store will often have the exact type of U-shaped tools you will need for removing many of the radio units in a Ford model.
Disconnecting the battery will activate the antitheft system. If you are reinstalling the same unit, you will need to input the security code so the radio will work again. Details of the code are included in the car's audio system's operating guide, and the dealer can often provide the code if you can provide proof of ownership.