Control - before purchasing a decoy you must consider how these products are controlled. Some of them are controlled by a jerk-cord; the best duck decoys are those that don't require the usage of the hunter's hands. Decoys should simply be turned on and then left alone to do their job. Another wise choice would be purchasing duck decoys that are controlled using a wireless remote control.
Power - power is one of the most important aspects you have to take into consideration before purchasing a duck decoy that is why hunters should always check to see how long the battery will last. A decoy with a low-life battery won't be efficient because you will have to change the batteries very often, thus scaring the ducks.
Paint - always avoid purchasing decoys that have a shiny paint as this kind of paint will reflect in sunlight and that, again, can scare the ducks. These kind of decoys aren't very realistic and surely you won't have a tremendous success on your hunting adventure.
Motion - search for those decoys that have a realistic movement as these decoys will attract more ducks in comparison to decoys that have no motion or decoys that have an unrealistic motion. The best decoys are those that use bobbing heads and flapping wings.
Water - if you plan on using duck decoys near water you have to make sure that these decoys won't become damaged, that is why you should always look for designs that have protected motors and wires. Even if you don't plan on using these decoys in water conditions, you should purchase decoys that are water resistant in case of a sudden rain starting during your hunt.