In warmer parts of the western world air con is a fixture - most people would consider it an essential for the home and the office. Many systems are past their best however, and many of us are looking for ways to improve cooling efficiency.
The first answer might well be simply to upgrade your system. If you have an older unit then the modern units with energy star ratings will offer significant improvements in efficiency - you could see around twenty percent sliced off you cooling bill.
Getting a new system installed also gives you a chance to improve your entire HVAC system. The newer and very popular gas pack heating cooling units are well worth considering.
If you do not want to splash out on new equipment, there are other things you can do. Maintenance is the first rule. A qualified engineer servicing your unit can make it work far more efficiently.
A quality programmable thermostat will make sure that you do not waste energy (and money) cooling the space while you are at work or whatever.
Within your air con system you should search out the gaps in the ducting system (most homes have them) and then seal them and improve and insulate them.
The final thing to think about is a ceiling fan. An energy-efficient fan (look for the rating) can run anti clockwise to help the cooling.