Filling your gas magazine

If you fill the mag and gas begins to spill or sputter, STOP. If you can’t detect or are not sure when the magazine is full, 6-12 seconds of filling the mag should suffice. If the amount you put in doesn’t shoot all the rounds, adjust the time accordingly. Allow the magazine to warm up to room temperature before attempting again. This is usually about 5-6 minutes. If you are able to form a tight seal and fill correctly, allow the magazine to warm to room temperature. When discharging your magazine, your impulse is to press the gas release valve usually located on the top-rear side of the magazine, causing all the gas to dispel at once. Do NOT do this!! Releasing the gas this way will not only wear out the seals faster, but it can freeze the O-rings in your magazine, damaging them permanently! The safest way to discharge a gas gun is to fire it until it runs out of gas, guaranteed.

Storing your magazines

After usage please leave or insert a small amount of the appropriate gas, enough for 2 - 3 shots is recommended. Do not keep them in storage while fully charged or completely empty. This will allow the O-Rings of the magazine to remain properly lubricated while in storage.

Temperature

Fire the gun in WARM weather. Use during the cold seasons is not advised. They will not cycle completely or fire well and will use more gas than normal. This is because in colder weather the gas loses pressure, and it will take more gas per shot to expel it from the barrel. Rapid-firing of the gas-gun will also cause the gun to freeze up, resulting in damage to the magazine or gun. Instead, fire the gun at a slow or steady rate of fire. These problems are not as prone to occur during the hotter seasons or warmer weather.

BBs

As with most high-tier or high-maintenance guns, you want to use high quality BBs whenever possible. This prevents jamming or other problems, and increases accuracy. In the case of almost all gas guns, .12s are NOT recommended.

Basic Maintenance

Even a little bit of lubrication after every use goes a long way to increasing your gun’s lifespan. Using 100% Pure Silicone Oil, you should lube the slide and any and all moving parts. If you ask around, most people would highly advise that you do not use: Hoppes #9, WD-40 or other petroleum based lubricants as will damage the guns permanently. Some “100%” Silicone oil brands actually have other chemicals that can also damage your gun. For a safe bet, buy oil that is recommended by most other airsofters, or buy oil specifically designed to be used in air soft guns. Be sure to also spray silicone oil into the top nozzle of the magazine well every 5-6 magazines uses. This is done by pressing the top release valve on the the mag while putting a quick spray of silicone into the top rubber exhaust valve. This will keep the seals and O-Rings properly lubed for a lifetime of use. For further information on how to lube your specific gas gun, refer to a manual or even better, look into it online, asking others who own the same gun as you on how to properly maintain your gun.

Gas Longevity

The amount of gas consumed and lost depends upon a few factors. Namely, the temperature of your environment, how much you are shooting, and the gun itself (it's design dictates how much gas is consumed per shot). Non-blowback guns use around the same amount of gas as Blowback, but since it doesn't expend gas on physically pushing a slide back or otherwise creating a blowback effect it can put more gas into actually propelling the BB.

HFC-134A

Other Names: Duster Gas, Air in a Can
This is the weakest gas available. It is common air, and is also known as duster gas. Cans of this can be found at most computer stores. It is possible to use this in gbb mags, with the purchase of an adapter. Stock TM pistols are meant to be used with this gas.

Green Gas

Other Names: HFC-22, "Top" Gas
This is one of the most common gasses. Most gas guns out there can use this gas without upgrades; one exception being TM's (explained above). Green Gas is simply propane with added silicone and added perfume (since propane smells like fried onions). This is why propane is almost always recommended (explained below)

Propane

Other Names: Camping Stove Gas, "Coleman", "Bernzomatic"
This is the same exact gas that is used in the small camping stoves. It costs about $3-5 a can, and is about as strong (maybe a little stronger) than Green Gas. In order to use propane, you simply have to buy a propane adapter, screw it on, and spray some silicone oil inside the adapter every ~4 mags. This is often recommended over Green Gas as it's cheaper in the long run.

Red Gas

Other Names: None
This is an airsoft-specific gas. It is stronger than propane/green gas, and brings lubrication and scent. Be aware that if you use this gas, your gun will degrade faster than normal. Also, some guns will not be able to handle red gas.

CO2

Other Names: "Black" Gas (up for debate)
This is the strongest of all the common gasses used in airsoft. Only guns made to handle CO2 will be able to use it, and even they will not last a long time. It is a VERY strong gas. These are the small 12g canisters that you find at a few sports stores, plus a few other places, and requires special CO2 mags since the canister goes in the actual magazine.