Everyone has a different method of changing brake pads the most commonly used method is to lift the retainer and pry the pistons back in and remove the old pads.  This procedure may be a little difficult with factory pads since there are the dome shaped anti squealing shims on the back of the brake pads.  The method showing here gives you much more room to work with and lessor of a chance you may damage your rotors. 

(1). Put the car on jack stands, please refer to "How to jack your car up" DIY section for details.

(2). Remove the wheel, remove the brake pad sensor wire from the holder by sliding the hold down first. 

(3). Use a vise grip pliers to squeeze the center of the brake pad retainer and use a flat screw driver to pry up the retainer. Once the retainer can be swing up you can remove the sensor wires from it.  And unplug it at the terminal.

(4). Unbolt the two caliper mounting screw 10 mm hex.  These pictures shows the upper and the lower bolts to remove.

(5).  A little modification at the brake line clip will make things a lot easier for you.  For some reason there are no opening at the  brake line holder on the strut, the only way for you to remove the brake line away form the strut is to loosen the brake lines which means you let air in the brake system and you will need to bleed the brakes later.  I found it to be much easier if you make a little modification to the brake line holder.  Use a Dremel motor tool with a cut off wheel attachment and make a opening for yourself.  This way you can slide the brake lines out from the strut and you would have no possibility of bending the brake line by accident when  working on the caliper.
The left picture shows the brake line holder with the clip, the clip can be lifted up by using a flat screw driver, the right picture shows the modification I made using a Dremel cut off wheel on the brake line holder.  Now the brake line can be easily moved away from the strut.

Here is a picture of the brake caliper completely off and can be easily worked on.   No coat hangers or wires to tie it up.    Use a C clamp to squeeze the pistons back in so there will be enough room to clear the rotors once the new pads are installed. Now you can remove the brake pads from the caliper, you may need to use a flat screw driver to pry it out from the pistons. If you added brake fluid in your reservoir because the fluid level went down since the pads were worn out you need to use a turkey baster to suck some out first, because when you squeeze the pistons back in the fluid level will rise and it may over flow the reservoir.  Also to remove the cap on the reservoir will help ease the process of squeezing the pistons back in. 

To remove the rotor you will need to unscrew the two Philips screw that holds the rotor in place.  Some screws may be rusted on, recommend using a impact screw driver to remove them.  Once the screws is removed the rotor will come right off. 

Information contributed by Ray Calvo from the factory shop manual:
 Torque the bolts 63 ft-lbs front & rear. The shop manual 
        also say to replace the front bolts whenever they've been undone.

For your first time DIY guys please read this important message from Ray Calvo first

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This is the "BRAKE PAD REPLACEMENT HOW-TO" contributed by 
Ray Calvo for the Allegeheny Region PCA newsletterletter

Somebody on "Rennlist" recently asked me my procedure for replacing brake pads on all 4 wheels in under an hour on my 993.  I thought I had written this up, but in doing an archeology dig, I couldn't find anything.  So, here goes!  I would think that a modification to this procedure could be used on any Porsche from about the 964 vintage.

First, a warning
Porsche on the 993 (and probably later water-pumpers) has installed some nightmarish anti-squeal reducers on their recent factory brakes.  The 993 pads included (see picture):

     - a fabric-like lining glued to the back of the pad backing plate. 
     - small cup-like attachments glued to the back of the pistons and the backing plate.

To initially get the pads out, I used a stiff metal scraper (like used for paint/grout/plaster scraping in the home) between the anti-squeal shim and the brake backing plate.  Then with the anti-squeal shim free from the pad, the pad could be pulled and the anti-squeal "junk" could be removed. 

Now on to the pad replacement.  This is what I use; vary to suit yourself:

- 2 1/4 ton floor jack with a hockey puck in the lifting cup (protects the body)
- 3/4" breaker bar with 6" extension and 19mm 6-point socket (I've had the 3/4" bar for 25 years; 1/2" should be fine)
- 1/2" torque wrench going to 150 ft-lbs
- battery powered screwdriver with 19mm socket
- flat/curved face pry bar (imagine type needed to open a wood crate)
- water pump pliers (called Chan-nel-locks in our family)
- old medium flat-blade screwdriver with a V-groove cut in the blade end
- old front and rear brake pad with all lining knocked off (all you want is steel backing plate)
- brake pad pulling tool (ATE type as shown in picture; more at end of this article)

OK, here we go!

1)  Loosen all lug nuts with breaker bar and 19mm socket (I don't have wheel locks; you might have to use the special socket if you have special anti-theft lug nuts)
2)  Insert hockey puck in lifting cup of the floor jack, lift up rear corner of car at lifting point (just in front of rear wheel arch; look for metal lifting point).  Keep raising till entire side (front and rear tires) are off the ground.
3)  Use the battery-powered screwdriver with 19mm socket to remove 5 lug nuts on a tire, remove tire.
4)  I am assuming all the anti-squeal garbage is off the pistons and brake pads.  Now, take water pump pliers and compress the brake pad hold-down spring.  Unclip the one end of the spring from the caliper (it should pivot from the top of the caliper).
5)  You will notice a cutout in the center of the pad braking material.  Insert end of a medium screwdriver in this slot and pry sideways.  You are trying to pry the pad away from the rotor slightly.
6)  Use the brake pad pulling tool to pull the pad out of the caliper.  If you don't have this tool, get some heavy wire and thread it between the upper and lower drilled hole in the pad, and grab both wire ends with a vise-grips and pull directly away from the caliper.  If you have pried the pad sufficiently away from the rotor in step above, it should come out easily. 
7)  Each pad will have an anti-wear sensor in it.  Remove the pad whole with the sensor attached then unplug the sensor wire at its location up on the suspension.
8)  Some folks have had success carefully prying out the sensors and transferring them to the new pad.  If my success rate was a batting average, I'd never get out of the minors.  I have given up on using the sensors altogether.  I have cut the sensor wire about 2" below the connector, stripped about 1" of insulation off each wire, then connected the ends with a wire nut and reinstalled this "cheater" wire back into the on-car connector.
9)  Now you have to compress the pistons into the caliper to install new pads.  Use an old pad and knock all the lining  off of it.  Now place the old pad backing plate in the slot left by the old pad, and  with the prybar between the backing plate and the rotor pry/push the pistons into the rotor.  MAKE SURE the pad on the other side is installed, and there are pads in all the other wheels (otherwise, you risk forcing a piston you're NOT prying against completely out of the caliper). 
10) With the pistons compressed, the new pad goes in easily.  Repeat on the other pad.  Now, compress the hold-down spring again and push in on the free end of the spring with the flat bladed screwdriver with the V-cut until the spring catches in the caliper.
11) Install wheel, install all 5 nuts and tighten cross-wise with the battery powered screwdriver.
12) Repeat for other wheel on same side of car, then lower car.
13) Repeat (2) -(12) on other side of car.
14) Torque all lug nuts to 90-95 ft-lbs in a cross-wise pattern.  I like to initially tighten them by hand to a firm snugness in a cross-wise pattern, then finally use the torque wrench to finish the job.

Finished?  Not quite!  Remember, pistons are full contracted into the pistons; you have to extend them to their normal position against the brake pads.  I pump the brakes slowly, trying never to go more than about half stroke on the brake pedal.  This could take about 10-20 pumps.  Once pedal is firm, car is ready for a test drive and a pad break-in (follow manufacturers directions). 

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MORE on the ATE brake pad puller tool:  I bought this back when the peanut-picker was in the White House.  As I remember, it was pretty universally available at most of the aftermarket Porsche parts houses.  Now, when I want to describe it, I can't find a source!!  Some "Rennlisters" noted that the tools available at the following sites were similar.

http://www.houseway.com.tw/autotool/undercar/undercar07.htm
http://www.lucastestequipment.com/brake/brake_8.htm