It is quite common for those that are learning -- and even some of those that have been climbing for a long time -- not to recognize a backclipped carabiner. It is important for both leaders and belayers alike to be able to easily recognize an incorrectly clipped draw. It is also important to quickly correct this once it is recognized.
One of the best ways to avoid backclipping is to practice the art of clipping a rope into a draw. Climbers should be able to do this with both hands, regardless of the direction of the gate. This is a great technique to practice while vegging in front of the television. If you can wire it at home, then your muscles will remember how to do it and will do it right.
The following video provides a quick lesson on clipping a rope to a draw. Be sure to obtain real instruction from a live person before doing this in an environment that has consequences...
--Jason D. Martin