The best way to avoid noise is to stop it from appearing in the first place, rather than relying on noise gates.
String noise
Strings that are not muted by your hand may self-vibrate. This can be caused by loud sound levels, high gain preamp settings, strong compression effects or feedback. By threading a fluffy elastic hair ribbon around the guitar neck, the open string noise is reduced drastically. The ribbon can easily be pushed behind the nut if you want to play open strings (see picture below).
Electromagnetic noise
Noise sources
Noise appears in all audio electronics, partly because they pick up electromagnetic fields from speakers, power cables, computer monitors, TV sets, flourescent lightning, electric motors, radio broadcast signals etc; partly because noise is generated by "friction" between electrons and atoms when electric current flows through a circuit. The latter goes especially for amplifier circuits, where not only the original signal (with its own noise content) will be amplified a lot, but more noise will be added in the amplification process itself. This is one reason why overdriving a signal makes it more noisy.
The amount of noise produced in an electronic device is indicated by its signal-to-noise ratio, which means the level difference in dB between audio and noise.
Different ways to avoid electromagnetic noise pickup
Once a signal has become "polluted" by noise it's hard to remove the noise content without altering the original signal, so it's best to stop noise from being generated as early in the signal chain as possible. This can be done in a number of ways:
The guitar is a very important source of noise, because the pickup signal (and its noise content) will be amplified hundreds of times in the guitar preamp. Especially guitars with single coil pickups work like antennas that easily pick up external electromagnetic noise. This can be avoided by shielding the inside of the pick guard and the pickup cavity using aluminium tape or electrically conductive paint (see guitar builder sites or -books for details about this) and by finding a guitar position (relative to speakers and other disturbing gear) that picks up the least noise. Humbucker pickups are designed to cancel out as much noise as possible. The same thing goes for two single coils on a strat used in the "middle" positions. There are also pickups available that sound like single coils but without being as noisy. Active pickups are less noisy than passive.
Make sure that the first tube in a tube preamp is of good, low-microphonic quality. This is were a lot of noise is produced in preamps, and where good quality tubes are the most important.
Use power conditioners that will produce "cleaner" electricity without as much voltage fluctuations and transients as in the average power supply.
Use balanced cables to avoid noise from being picked up by the cable. Balanded cables are standard equipment for PA microphones but have never been used widely for guitars. The G-Force features balanced outputs, that can be used when connecting it to a mixer, but this is far less important than minimizing the noise pickup from the guitar or preamp.
Avoid groundloops in your equipment. Preventing this can be done in a number of ways:
By enabling the "ground lift" switches sometimes found on audio devices.
By isolating each piece of rack equipment from a metal rack frame with plastic bushings, or by using a rack frame that does not conduct electricity.
By adding isolation transformers in the signal path.