The earliest vacuum pots appear to be first used in Germany in the 1830's. England and France followed suit soon after, and the siphon quickly swept across European aristocracy. The syphon functioned to serve coffee, but doubled as entertainment for guests, and "bestowed prestige upon the hostess," according to Brian Harris's account of coffee history.
Made Easy by Mark Prince:
Fill the bottom vessel with hot water, then place the filter at the bottom of the upper chamber. You can use cold water if you want, but be warned it will take considerably longer, and water will seep into the siphon before reaching the optimal temperature for extraction.
Wait to grind your coffee until right before you pour it into the upper chamber, ideally slightly finer than drip.
After this, you insert the upper chamber into the bottom one, carefully so as not to chip the siphon. Most sets come with some sort of rubber gasket or something to seal the center, ensuring no air will escape where it isn't supposed to, allowing suction into the upper chamber.
Now all you need is your heat source, whatever it may be. A stovetop will do, or any burner as long as it has an adjustable flame. Crank the heat up to high to start. As the water evaporates it expands, causing pressure to build in the lower chamber, pushing water up into the top.
As moisture begins to seep upwards through the filter, be ready with your stirring stick, because you want the grounds completely saturated. At this point you can lower your flame a little.
Continue to stir, and be sure to keep a constant eye on the flame. The idea is to maintain just enough heat to keep the water in the upper chamber, but it should never be boiling, just brewing.
The steep time depends on the size of your siphon. Generally speaking, the steep time for a single serving should be no longer than a minute and a half. Like I said, try to maintain the minimum amount of heat necessary to keep the coffee at in the upper chamber for the duration of the steep time.
Once your coffee's done steeping, remove your heat source (if possible, obviously not if it's fixed to the siphon) just in case of any residual heat after turning it off. This part is called the kick down. As the bottom vessel begins to cool down, the vapor condenses back into a liquid, causing the coffee in the upper chamber to drain, passing back down through the filter and filling the lower vessel.
Finally, you just dissemble the siphon and enjoy your coffee.
Surprisingly, you can vacuum-brew your own coffee, for instance with this one from Sur La Table. It takes only five to ten or so minutes to whip up a spectacular batch of coffee so good it defies the laws of physics. Plus, who doesn't like showing off their awesome new anti-gravity coffee brewer to guests? It's entertaining and lets you feel like a scientist for a minute, so what's not to like?
Bon'Cui.com boasts the ValBeMar butane burner below an ideal heat source for the syphon, complete with an instant electronic ignition and adjustable flame.