Turn off power to the circuit
Remove the fuse from its holder
Inspect the fuse element for a visible break, burn mark, or melted spot
Check a glass fuse for a darkened or cloudy interior
Use a multimeter set to continuity mode
Touch the meter probes to both ends of the fuse
A continuous beep or near-zero resistance means the fuse is good
No beep or infinite resistance means the fuse is blown
Compare the fuse to a known good spare of the same type and rating
Replace the fuse only with one of the same amperage and type