1) Shipping gear inside a metal rack cabinet: Plain and simple, most metal rack cabinets are not meant to be shipped with gear racked into them. These cabinets are meant to be in a fixed location and at most, only wheeled from room to room. People assume that if they crate them for shipment, with some foam protection around them, they will be safe. In actuality, the case and the gear can get severely damaged in transit due to vibration and shock. The heavier the rack gear, the more danger involved. If you need to ship your cabinet, remove the gear and pack it separately.
2) Using a box-inside-a-box fabricated shock rack case: Many case manufacturers make shock rack cases that consist of an outer box foam lined to hold an inner fixed rack box. Without delving into the particulars of foam cushioning curves, the problem here is that too much foam is being used to provide any actual shock protection. This system does an adequate job of vibration protection, but will not create the slow deceleration needed to dampen external shocks. A much better alternative is a true shock mount cage with shock absorbers in the corners.
3) Leaving the wheels on the case during transit: The correct thought here is that the case will most likely remain upright if your shipper can roll it around on its base casters. This is true, most of the time. Wheels, however, are the most common item that gets broken on cases. If your wheel does break, your rack case has a very good chance of falling over, or constantly banging on the the base. Another problem is that uneven flooring can cause a wheel to abruptly catch as the case is being pushed around a shipping dock, thereby tipping it over. A better strategy here is to have a caster storage pouch inside the lid, and stow the casters during transit. With regard to handling by the shipper, using an inexpensive tilt indicator is a better deterrent than leaving the wheels on if your goal is to keep the case upright.
4) Not using the right load range shocks: If the person selling you a rack case does not ask you how much weight is going into the case, beware. All rack case shocks are not created equal. Having the proper load range is essential to countering shock and vibration during shipment. If you are not sure, or if your equipment set has changed since you bought the case, ask a professional for advice.
5) Not securing the contents of shelves and drawers: Just because you are using a shock rack case does not mean that items in your rack drawers and on your shelves will not get jostled around. Use separate cushioning inside your drawers, and use a securing strap or brace for items sitting on the popular Velcro rack shelves. Rack mount keyboards are particularly sensitive, and you should check with the manufacturer to see if they can be safely shipped. Otherwise, you may be picking up keys off the bottom of the case.
6) Using a rack case with inset edge casters: Several manufacturers have recently come out with pull-along rack cases that feature telescoping handles and edge wheels. There are fine for moving cases around on carpeted floors, but typical shipping environments are very rough on them. It is also very likely that these cases will be upended, dropped, or even tossed like luggage. Rough treatment can defeat even the best of shock systems. If you own one of these, consider skidding it for shipment.