'96 Chrysler Concorde - takes multiple tries to start

My '96 Chrysler Concorde has been having a lot of trouble starting since I got back home from college. My sister has been using it and has reported that it takes several tries to start it. Whenever I try to turn the key in the ignition, there is a clicking sound and the radio/lights come on, but the engine will not start. Sometimes it takes two tries, others it takes several dozen before the engine will start. How do I resolve this issue?