Experience

A song is a means to communicate with an audience. To relate with them an experience they too have likely had but did not articulate into lyrics and melody.
The actual song writing part of song writing typically happens late in the process. First comes an experience that provides inspiration to create a "short story" worthy of a listener.
      
With every moment that passes you have an opportunity to witness and record inspiration. The still calm of a late summer morning. A child's chalk drawing on the driveway that spills out on too the road. While dinning outside on the avenue, an old, beat up car passes by with a creepy doll strapped to the front bumper and the driver stares at you as they pass. (wish I was kidding....happened last night!) Hoping for an enlightened moment will more often leave you with less inspiration. Seek and you will find.