Air conditioning maintenance, for the most part, is all about cleaning. That said, you could do most of the maintenance yourself. It saves the HVAC contractor/technician a good chunk of time if you have already done this part of the maintenance. Here is what you will need and how to do it.
Warm, Soapy Water and a Rag or Sponge
Take these items outside and wipe down the condenser box. Try to get in between the slats, if they exist in your condenser box. If you cannot get to the box because there are weeds, plant growth, and/or spider webs around the box, you will have to remove all of this first. Then wipe down the box as thoroughly as you can. Avoid the area where the A/C's electric cables exit the box.
Completely Clear the Area of Grasses, Climbing Vines, and Weeds
Even if you did not have a technician coming to do the rest of the maintenance, it is still a good idea to clear a four-foot area all the way around the box. Since you do have a technician coming, clearing the area also helps him/her get close enough to the box to remove the top and get inside. Avoid mowing around the box unless you have it covered up because the cut grass can fly into the unit and cause problems inside.
Pull the Outdoor Fuses and Check Them
There is an outdoor fuse box for central air conditioners. Open yours, pull the fuses, take them to the hardware store, and ask to have them tested. If they register as having enough power, you can reinstall them in the outdoor fuse box. If the store associate says you are dealing with dead or nearly dead fuses, buy replacements and install the replacements.
Change the Furnace Filter
Most central A/C units operate in conjunction with your forced air system, which is also part of your furnace. As such, you should replace the filter while you are doing a majority of this maintenance work yourself. It is a quick and easy thing to do, and one you would have to do anyway. While you are at it, clean the area around the slot where you have to install the furnace filter. This clears away extra dirt and dust that can clog up the filter. Keep the area around your furnace as clean as possible to provide higher quality air to your home.