Most people don't notice their air conditioning units until they stop working. Avoid that headache by cleaning and conditioning your unit. First, turn off the power.
Step 2: Get a Trim
Trim back any shrubbery and remove and leaves, lint or dirt from the outside condenser.
Step 3: Top Off
Remove the top cover with a drill.
Step 4: Comb It Out
If the fins are bent, use a fin comb to straighten them.
Step 5: Hose It Down
Clean the evaporator condensor coils by removing access panels, and use a strong spray from a garden hose to clean it.
Step 6: Clean It Up
Clean the fan blades and dust/vacuum around the motor.
Source: GMC Trade Secrets