1. Consult your owner's manual: This will have diagrams showing the location of major components.
2. Look for the large, cylindrical component with several belts running to it: This will be the compressor. It's often connected to the power steering pump and alternator.
3. Trace the AC lines: The refrigerant lines (usually thicker and have a distinct look) run from the compressor to the condenser (usually located in front of the radiator) and other AC components. Following these lines will help you find the compressor.
Keep in mind that working on car AC systems requires specialized tools and knowledge of refrigerant handling. If you're not comfortable with automotive repair, it's best to have a qualified mechanic diagnose and repair any AC issues.