If your brake pads are worn, you'll start hearing them moan or you will see the wear indicator disappear.
Some people use a tool to hone them again, some people use scotch brites. Some people just wash it with rotor cleaner. I cleaned the rotors with some simple green and scotch brite and beded them in according to my preferred method. If you dont clean your rotors your not going to get the pads to mate with the rotors and your brakes will feel like they don't even exist.
Step 1. Remove the 2 bolts and press the caliper against the rotor to compress the pistons, otherwise you wont be able to get them out. Read on and youll see what i mean.
Step 2. Remove the 2 cotter pins that hold the main pins. I like to use a pick, if you cant access it, you can rotate the pin by hand or with a pair of pliers. there are 2 cotters per brake. One on each pin
Step 4. Looking at your pads. Heres some pics of my old pads vs new Pads You can see the difference here.
Step 6. Using a prybar, screw driver, whatever you have around you that can give you leverage to push the edge of the piston in. Becareful as you can make a scar on the brake caliper if you dont put a piece of clotch between whatever tool your using and whatever part of hte caliper your pushing against for leverage. Dont go nuts here, once the pistons start moving just let it move slowly.
Step 8. Like previously, you just reinstall the pins so they pass through both pads, and the backing plate. Notice that the backing plate as an UP arrow indicating which way it should be installed. Reinstall the cotter pins and then use a screw driver to gently spread the pads apart so you can slip the rotor between them.
Now slip it onto the rotor reinstall the 2 bolts and your good to go.