Figure out if you need to change your car brakes by using the sight and sound test. On most cars, you can check for brake pad wear by looking through the openings on the front tire rims. You should replace the front brake pads if the pad depth is less than a 1/4 inch. Don't wait any longer or you risk ruining the brake rotors, which are very expensive to replace. You can also test the brakes by taking a drive and paying close attention to any sounds being produced by the noisemaking shims attached to the brake assembly, which let you know when it's time to replace the pads. If you hear a screeching sound when you press the brakes, it is time to change the front brake pads.
Park the car on a flat cool surface like a shaded, paved parking space if you don't have a garage. Use the four wood blocks to keep the rear wheels from rolling backwards when you jack up your vehicle. Make sure the car is in park and that the parking brake is properly engaged. Use the tire iron to loosen the lug nuts on the front tires. Slip the jack under the car--a hydraulic jack is best if you've got it--and find a flat spot on the frame near the rear of the front wheels or the end of each axle to raise the car. Place the jack stands under the right and left ends of the front axle and lower your auto onto the stands.
Grab the tire iron and remove the lug nuts from the driver's side tire. Leave the passenger side tire on. Once you have removed the first tire you will see the disc brake assembly exposed. It is made up of the caliper, two brake pads, a rotor and bolts and clips that hold it all in place. Remove the bolts holding the caliper, which is the large metal object that presses the brake pads into the disc rotors. Slide out the caliper to reveal the brake pads, which are held in place by a bolt or clips. Remove the bolts or the clips while holding the brake pads in place. Pull out the used up brake pads.
Before installing the new brake pads, you have to reset the piston located along the back of the caliper. Use the heel of your hand to pus the piston toward the center of the car. If that doesn't work, use the vise-grip of a C-clamp.
Rub brake lube on the new brake pads and place them into position on either side of the rotor. Secure the pads in place with the bolts or the clips. Close the caliper by tightening its bolt and put the front driver's side tire back on. Go to the passenger's side and repeat steps 3 through 5.