98 Chevy 1500 truck won't start when cold?

First thing to have checked is your battery! See if it is fully charged and holding a charge. Check simple things before moving to more difficult. Check your glow plugs ie( heating plug) weather its working or not if it fails u 'll face this problem. u can check with battery and a wire with passing the current. if the spark is produced in glow plug it works or it does not . any quires let me know