As with other emergency situations, a seizure (especially a violent one) could drive witnesses to panic. It is therefore very important to calm down everybody and maintain one’s presence of mind. The seizure could last from only a few seconds to a few minutes, and such a short amount of time could already cause some damage if the situation is not handled properly. So it is imperative to act quickly and be decisive, and most importantly, to remain calm.
During a seizure, clear the area around the person who is having a fit. Common sense would come in handy here. Remove or push away any object that might cause injury (furniture, appliances, and chairs). Reassure everyone nearby that the situation is under control despite what it may look, and request them to give the person some room.
Among the most immediate medical concerns during an epileptic seizure is respiratory obstruction. So ease the person on the floor, place some cushion (any folded clothing or jacket) under their head, and loosen clothing around their neck (remove eyeglasses, neck tie or any head gear the person may be wearing). The point is to make sure that they are breathing properly.
Let the seizure spend out itself. Which means you should not restrain or hold down the person while they trash around as the seizure progresses. You cannot stop it, so don’t. Of course, you should also watch out for yourself and avoid getting injured.
Perhaps you’ve seen movies (the French film the ‘Brotherhood of the Wolf’ comes to mind) in which people try to insert some object (a piece of wood or comb or—gasp!—the wooden handle of a knife) in the mouth of the seizing person, apparently to prevent them from “swallowing their tongue.” This is a “popular” or pervasive fallacy: no one can swallow their own tongue. So don’t go yelling, “Give them something to bite!”