After checking battery for full charge then do as oldwizard suggested. Also using a simple volt meter check for alternator proper charging and bat condition. Sometimes there is enough juice to turn on dash lights but not start the vehicle because of bad/corroded cables at the terminal or low bat charge.
I carry in all 3 trucks a small grey in color gizmo (volt meter???) with a black and red prongs and colored lights to denote condition of battery and if alternator is charging the battery when engine is running. Green is good, yellow is fair and red is dead. Alternator should be putting out at least 13.5 to 14 volts to proper charge the bat. I buy these cheap gizmos from auto zone, Napa, and O-Reilly's and been using them since at least 2001 and they have saved me from being stranded in remote areas.