best way to fix air conditioner?

What's it doing, not cooling, not turning on, or leaking? The free checks first: thermostat set to cool and below room temperature, breaker not tripped, filter not clogged (a filthy filter causes a surprising amount of 'broken' AC). Outside unit, make sure it's running and the fins aren't packed with leaves and fluff. If water is dripping inside, the condensate drain line is probably blocked. Past that, if the outside fan won't spin or it hums and clicks, it's often the capacitor. That holds a charge even with the power off, so I'd leave that one to a tech.