Summarize:

There should be an outdoor shutoff near the condenser unit. This will resemble a square box on the wall of the apartment or house. Inside, look for a switch that you can slide to the "OFF" position. If there is no switch, you'll need to manually pull the plug which feeds power to the condenser. Before you begin disassembling any portion of the condenser, it's crucial that you disable the power supply. If you cannot find the power outlet where the compressor unit is plugged in, or if you're inclined to be extra cautious, you can simply flip the switch to "OFF" in the circuit breaker box which controls power to the AC condenser. The fine, narrow slats of metal which line the sides of the compressor unit are called "fins." You can clean the fins by running the nozzle of a vacuum cleaner over them; this will remove the debris and allow the condenser to pull in air without obstruction. A wet/dry vacuum is the tool best suited for this job. The condenser unit sucks in air through these fins. Over the course of time, these will become dirty with bits of leaves, grass, and dust. If you don't have a wet/dry vacuum, see if any of your friends or neighbors have one. You may also be able to rent a wet/dry vacuum from your local hardware store. Often with normal wear, some fins on the condenser can become bent. If you notice that any of the fins are crooked or have been twisted, you can use a knife or kitchen utensil to gently straighten the fins. Apply gentle, steady pressure to bend the fins back into position. If you use excessive force, you risk snapping off the fins or damaging them further. The fan unit sits on top of the compressor, and is typically covered by metal wiring or a grate. Using a screwdriver, remove the wiring on top of the fan, and then unscrew and remove the fan itself. Due to the wires connecting the fan motor to the compressor unit, you may not be able to fully lift off the fan. You'll simply have to lift the fan as far out of its housing as possible. Using your garden hose, rinse any debris (bits of leaves, grass, dust, or pollen) from the blades of the fan. To make sure that the fan blades are clean, you can also wipe them off with a clean cloth or rag. Then, use the hose again to spray water through the compressor's fins from the inside of the unit. Rinsing the fins from the inside will make sure that any obstructions are cleared, and the unit can effectively draw in air. Once you've finished cleaning the fan blades and the interior of the compressor, you're ready to put everything back together. Set the fan back in place, and re-insert the screws holding it to the metal frame. Do the same thing with the metal wiring over the top of the fan. At this point, you can also turn the power supply back on.
Shut off power to the unit. Vacuum the condenser fins. Straighten the condenser fins. Unscrew and remove the fan. Wash the fan blades and the interior fins. Reassemble the compressor unit.