Make sure you have the number to a local plumber near by, this again is just in case, it is easier to have a number handy than trying to look one up in an emergency. You should also plan your project when the local hardware store is open, in case you need additional parts, or tools. There are two types of faucets, the two handled compression faucets, and the single handle non-compression, or washerless faucets. Most leaks are located in compression faucets because of the way they are designed, so the following will apply more to that type than the washerless. Next determine what brand name faucet you have.
Most faucet parts are interchangeable, but a few are brand specific.
You are almost ready to start, so get your tools together. A screwdriver, both a standard slotted and a Phillips or a cross top. You should be ready now to shut off the water supply to the faucet. Turn the water off and then open the faucet to drain any residual water out, this will also let you know if the faucet is truly off, or just almost off. Once all the water is drained you will be ready to start your repairs.