If a fuse blows or a circuit breaker trips every time you turn on a switch, the switch itself is probably to blame and should be replaced. There are many different types of switches, but replacement procedures for most of them are very similar. You may wish to substitute a different type for the faulty one; for example, replacing an ordinary switch with a mercury (silent) type.
Make sure the electricity is turned off before beginning to work. Either remove the fuse, or trip the breaker serving that circuit. Remove the two screws holding the cover plate, and lift off the plate. Remove the mounting Michael Kors screws holding the switch to the wall box, and pull out the switch.
Carefully note the wiring of the switch. It will depend on where the switch is located with regard to the rest of the circuit. Wiring for a three-way switch (where a fixture can be controlled from two separate locations) is somewhat more complex, so make sure that the new switch is wired in the same way as the faulty one. If space permits, transfer one wire at a time from the old to the new so that you get them right the first time. If you don’t have any space, label the wires with masking tape and a pen so you can remember which one is which.