Here are a few things you can do to maintain your air conditioner.
Change your air filter regularly. Check your unit's air filter once a month and clean or replace filters as necessary. Keeping the filter clean can lower your air conditioner's energy consumption by 5% to 15%. Ask your service contractor to show you how to do this, if you aren't familiar with the process.
Keep your condensation line clear. Condensate lines drain away the moisture your air conditioning unit creates. A plugged condensate drain can cause water damage in the house and affect indoor humidity levels. You can help keep the line clear of mold and mildew by pouring in a small amount of household bleach. Ask your service contractor to show you how.
Use a programmable thermostat. Programmable thermostats not only save you money, but they save your HVAC system from working overtime as well. Programmable thermostats allow you the luxury of programming the timing of your ideal climate throughout the day. Have the AC turn on an hour before you come home from work, and your house will be cool for your arrival. Not to mention, if you do decide to manually adjust your thermostat, don't feel you need to go to polar ends to get the house to cool down. If the temperature outside is 95 degrees, and you want to cool down the house, your house will not get cooler faster if you set the thermostat at 65 degrees rather than 85. Don't feel you need to push the thermostats to extreme ends to get your end result. Many people will forget to turn the AC back down once the house is cool, and it costs your system and wallet in the long run.
Schedule a routine service for your unit. It may cost you a little money in the long run, but in the end it will save you money. Routine service visits can save you thousands. Having your unit routinely serviced will help it run more efficiently over time, and will typically prevent system break-downs. Many people don't take this into account, but if your HVAC system fails during peak service times (i.e. summer), your visit will usually take much longer to schedule (because HVAC experts are jam-packed with appointments) but it will also cost a premium price, because - you guessed it - it's a "peak" season.
Check List: What's included for air conditioning / heating system(s):