If you want to keep your air conditioning unit running efficiently, make sure you replace or clean the air filter once a month. Check the owner's manual on the a/c for instructions on how to clean the filter. Never run the unit when the filter is removed and let the filter dry before reinstallling it.
Cleaning the blades and coils will help the system run better. Make sure your power is off before doing more than cleaning, such as working on the unit. Also, make sure you remove any debris or leaves from the condenser unit outside.
Do you hear a clicking sound when your fan is turning? This may mean that there is something in the way of the blades of the fan. If it gets so bad that the blade bends, you must replace it, just unbending it will leave the fan unbalanced and can cause further issues.
Make sure the equipment you are buying is ENERGY STAR compliant. It may seem a small thing, but it isn't. Products that are ENERGY STAR compliant can save you a lot of money in energy costs over the year. It can be over $100 easily, sometimes a lot more.
http://www.youtube.com/watch?v=-lO4xAsTyqM
