As sad as this may seem and no matter which despatcher you use (and I mean all!) labels, signs and any plea you can think of makes no difference. Fragile - this way up - handle with care etc etc is unfortunately a waste of a label or ink.
Make the packaging bullet proof and transportable at ANY angle, you'd be amazed how many times items are screened, handled, sorted, transferred etc before they get to their intended destination, and remember yours is only one item, it'll be stacked and shipped amongst thousands, especially by air - breathing space is not wasted!
Don't mean to sound gloomy, despite all most items arrive ok, damage is a very small % on the scale of things, but it does happen and insurance can't replace some things. Good packaging is everything.
Regards, Tony.