Generally, they are located:
* On the frame rail: This is a common location, often near the fuel tank, but could be anywhere along the frame rail.
* In the engine bay: Less common but possible.
To find it accurately:
1. Consult your owner's manual: This is the best resource. It will show the exact location and provide diagrams.
2. Use a repair manual: A Haynes or Chilton manual specific to your year and engine will have detailed diagrams and instructions.
3. Search online: A search for "[your engine] fuel filter location 2000 GMC/Chevrolet [truck model]" (replace the bracketed information with your truck's details) should yield images and forum posts showing its location.
Important Note: Be aware that working with fuel systems involves flammable materials. Take appropriate safety precautions, including disconnecting the battery negative terminal before working on the fuel system.