Never have FRAGILE on the box, this means stomp and run over with the truck to USPS mail handlers.
Fragile can also suggest "valuable" so I never use it. Only labels that go on any of my packages are the postage and if an additional one is needed to comply with the various Federal/Courier guidelines (ie: Lithium Batteries, Ammunition ORD-M, etc). And I never inform of contents unless it's necessary for me to do so, like with liquids/hazardous/etc, and those usually aren't my areas of dealing.