when sneaking around in a cardboard box it is easy to get caught and easy to hide. Simplicity wins all huh? Well, if you know how to use this technique you will be a master. Lets say your in the box and an enemy approaches you. When he kicks the box or looks in take off the box and pull the melee combo then tranquilize. It is effective for all modes except extreme of course.
Staying hidden is another thing, just stay out of the path the guard walks threw or set the box up in a formation with other objects (saved me multiple times). If you get caught, you now know what to do.
In alert mode this will not work. But if you are sighted and run around a corner or into another room and take a seat in the box, set up the scenery if possible and brace yourself. Then your set
Play sneaky but have fun ( DO NOT USE C4 ON AN ENEMY'S BACK FOR FUN!!!)^.-