Connect a noise suppressor or noise gate to the signal chain of a musical instrument, often a guitar, and set its threshold, typically with a knob and/or pedal, to eliminate any noise outside of that threshold from the signal. Normally, you connect the noise suppressor to the chain before the amplifier and any delay or reverberation effects. Slowly adjust and test the threshold settings to achieve a satisfactory sound with minimal noise.
Having a noise suppressor towards the end of the signal chain may be detrimental to certain high-noise effects. Certain noise suppressors solve this issue by allowing the effects loop to be connected to the suppressor between the input from the instrument and the output to the amp. Some examples of noise suppressors featuring this send and return loop functionality are the Boss NS-2, the TC Electronic Sentry and the ISP Decimator G-String pedals. This arrangement offers superior control over the signal being produced by the entire setup; most notably, it allows more signal from the instrument to pass through to the final sound while still allowing various effects to be applied.
To set up a noise suppressor, start by connecting the entire effects chain other than the delay, reverberation and amplifier. Connect the instrument to the noise suppressor input, and connect the delay, reverberation and amplifier to the output. Then, connect the beginning of the effects chain to the send jack on the noise suppressor and the end of it to the return jack.