Having had an independent specialist http://www.chillywillys.org to sort out my air conditioning earler this year (ended up getting a new condenser and compressor which was a financial ouch ) I was given the following guide from them which you may find of interest.
ON A HOT DAY
Switch the engine on, lower the windows to allow the heat to escape, turn on the air conditioning, build up the fan speed to maximum. Always use the air recycle option for the first ten minutes of every journey, when the vehicle is stationary or in heavy traffic. As the cabin temperature cools, raise the windows and turn down the fan speed to a comfortable level.
ON A WET DAY
Moisture in the vehicle, brought in on damp clothes and shoes or by other means has no way of escape, opening windows and vents allow more of it in. Using your air conditioning with the heater will remove the moisture in the air. Avoid the air recycle option as this will slow down the process, opt for fresh air. Within minutes, the windows will remain clear, providing a much safer driving environment.
Exercise the air conditioning in the winter by running the heater from hot to cold. This will burn off any external bacterial build-up on the evaporator. Any build-up in this area will aloow fungus to thrive, evident when a nasty odour is experienced in the cabin on opening or closing the air conditioning.
AND FINALLY
Always use your air conditioning - at least once a week or a few times each month. You get the best from from the system by being used regularly.
Also air conditioning deteriorates naturally by 10-15% per year and should be refreshed every two years.