If the vehicle has a lot of equipment in the trunk, or for whatever reason is heavily loaded to the rear, that vehicle has a great chance of losing control. In most scenarios there is nothing much you can do about having a vehicle loaded in that manner, but the driver needs to be aware of what can happen.
Another problem with backing up is knowing what to do with the steering wheel. The correct direction in which to move the wheel while in reverse can be very confusing. Actually the problem is mainly perceptual. The correct way to move the wheel is really quite simple: move the top of the steering wheel in the direction you wish the car to move. It's actually no different from what you do while driving forward; it just feels different in reverse.
While this may sound a bit foolish, make sure the car has come to a complete halt before you put it in reverse. Dropping an expensive transmission out of a car by slamming it into reverse can ruin your whole day. Keep a foot on the brake while putting the car in reverse. There's nothing like shooting out of a parking space and into the path of an oncoming car to add a little spice to daily life.
Make sure you are able to reach all your car's controls. It's a little foolish to hike yourself up in the seat for good visibility, put the car into reverse, and then discover you can't reach the brake pedal!
Short people have a hard time backing up because they have a hard time seeing over the back of the front seat and out the rear window. If you are short, position yourself as best as you can, making certain that you can see out the rear window and access all the car's controls.
Try to always park the vehicle so you will not have to back up to leave the area.