One common point of confusion with en garde is what to do with your non-sword (typically left) hand. Most people imagine the traditional pose, with your hand above your shoulder, wrist limp, fingers hanging loose. This works well enough, and is the traditional method, but the only real requirements are that you don't tense up or cover target. Tensing up slows down your reactions, shortens your lunge, does awful things to your ability to fence. Covering target prevents your opponent from hitting you. It will get you anything from a warning to a point for your opponent. It can also get you a nasty bruise or broken bone if you catch a particularly fierce attack with it. (It often has no protective padding whatsoever)