Change air and fuel filter then add some fuel injector cleaner to gas tank.
Possible vacuum leak along the intake manifold gasket. Another thing would be the Idle Air Control Valve, or the Throttle Positioning Sensor.
The answer I gave you is good for general maintenance but would agree with Rowefast on the problem you are having.
Looking for a Used C/K 1500 in your area?
CarGurus has 718 nationwide C/K 1500 listings starting at $800.
Search Chevrolet C/K 1500 Questions
Chevrolet C/K 1500 Experts
Related Models For Sale
Used Cars For Sale