First, choose good fuel. Avoid "regular" butane and only use isobutane/propane blends. In the US, Snow Peak, MSR, Brunton, and JetBoil should be fine. Don't get Coleman, Optimus, Glowmaster, or Primus for cold weather use.
Second, start with a warm canister. Keep the canister in your bag/quilt at night or in your inside jacket pocket (or something) during the day.
Third, keep the canister warm by placing the canister in water. If you chose good fuel in the first step, your fuel vaporizes at least at 11F/-12C. Liquid water will always be above 32F/0C -- that's about 20F/10C degrees above the vaporization point of the fuel. As long as that water stays liquid, you'll have good canister pressure, even if the air temperature drops below the vaporization point of your fuel. It's the fuel temperature that matters, not the air temperature. There are other ways to keep a canister warm which you can read about elsewhere, but water is safe and effective and is my preferred method. WARNING: Do not use hot water. Tepid is fine, but hot water may cause your stove to flare.
That's it. Choose good fuel, start with a warm canister, and keep the canister warm. Happy cooking. :)
Related articles and posts:
- Cold Weather Tips for Gas Stoves
- What's the Best Gas for Cold Weather?
- Canisters, Cold, and Altitude: Gas in a Nutshell
- Gas in Cold Weather: The Myth of "Fractioning"
- Canister Stoves 101: Thread Care
- Gas Blends and Cold Weather Performance. (Why not just use propane?)
- Gas Stoves: How Cold Can I Go?
- The "SuperGnat" (Camping Gaz or threaded canisters with one lightweight stove)
- Backpacking Gas Canisters 101
- Gas in Extreme Cold: Yes or No?
- Stoves For Cold Weather I (Upright canister stoves) -- Seattle Backpacker's Magazine
- Stoves for Cold Weather II (Inverted canister stoves) -- Seattle Backpacker's Magazine