How do you know what's wrong if your truck clicks when you try to start it then it finally starts?

These answers by mechanics about dead batteries are amazing me. I am a girl...really into cars because I have had a few. I just had this problem in my 1989 classic Saab. The problem is your starter...The clicking sound means that the pin inside of the starter is not projecting itself and thats why when you turn your key you hear a clicking. Get your starter tested