Could you describe the Soufflé technique? What pitfalls should you avoid? 
The key to any Soufflé is the egg whites.  The air bubbles trapped inside of them is what causes the mixture to rise.  (As daniel mentions McGee puts it at somewhere like 25% due to the air expanding from the heat and 75% from the steam interacting with the bubbles.)    Problems occur because the Soufflé is so reliant on steam and the egg whites setting.  If the base dilutes the egg whites then they can't set properly and the bubbles trapped inside of them can't do their job of making it rise.  If the whites are just mixed into the base thoughtlessly most of the foam will be destroyed.  Most recipes agree that stiff but moist and glossy peaks are how the egg whites should be beaten. 