Finding a bad light switch is not too difficult. It is a process of elimination. Make sure you check the simple things first. Is the bulb bad? Sounds silly but, you can get a bad bulb fresh out of the package. Try it with a bulb you know is working. Is the breaker tripped?

Use a non-contact voltage tester to see if you have power to the switch. Do you have power to the switch? You're sure the bulbs are good? The light still does not work? Yes to all three means that the switch is no good and needs to be replaced. The good news is that wiring a light switch is not hard at all. See The article 'Installing a Light Switch' for specific instructions. Just want to replace the switch? Follow the same link, it's pretty much the same thing.

Before you replace the switch, make sure it is not a loose wire. Turn the power off to the switch, put tape on the breaker (so no one will turn it on). Take the switch plate off and remove the switch from the box. Check for loose or corroded wires. Clean them up or tighten them as needed. Turn the power back on. Does it work? Problem solved. No need to engage in wiring a light switch.