When the play you're performing in calls for your character to pass out in a scene, learn to "faint" convincingly so you'll wilt and hit the stage realistically. As you're acting out the scene night after night, you also want to keep your falls injury free.
Instructions
1. Show signs that you're going to pass out before you actually fall. Blink your eyes as if you're feeling dizzy, breathe heavily, place your hand on your forehead or slow your movements and speech, for example.
2. Fall to the side so you can subtly roll your ankles, bend your knees, bend at the waist, "sit" on the floor and then let your body collapse onto the ground. With practice, you'll be able to perfect a fluid movement that also prevents your head from hitting the stage. If your character is sitting in a chair, simply go limp and slide onto the floor.
3. Ask a fellow cast member who will be standing next to you on stage to brace your fall. Even if the fainting spell is supposed to be a shock to the other characters, most people would have the reflexes to try to catch someone as they fall. Having someone grab your arm as you pass out can smooth your landing significantly. Perhaps you can improve the scene by passing out "onto" another actor so he'll react with genuine surprise.
4. Consult the wardrobe department about adding a little padding to your costume on the side of your body that bears the brunt of the fall. Talk to the stage manager about placing a rug or mat in the spot where your head will hit so you won't have to be obvious about holding it up a little as you faint.