Even if you are more than 5 nautical miles from an airport, there may be training areas where pilots frequently practice ground-reference maneuvers and emergency procedures. These can occasionally bring manned aircraft below 500 feet AGL and into the section of airspace that you may choose to fly your drone. Since most pilots operating in these practice areas tend to announce their position relative to the closest airport, having an air radio tuned to the local airport CTAF will keep you informed and improve your awareness of other aircraft in the airspace you share.
Also, familiarize yourself with local airport procedures, because it can help you avoid an accident. Such information can be found in an FAA Airport/Facility Directory (A/FD) or on a website like www.airnav.com