Children can add great value to every sort of movie. Examples include “The Sixth Sense,” “ET,” and “Beasts of the Southern Wild.” Unfortunately, an awkward performance can ruin a film quicker than a shaky camera or bad sound. If you’ve found a natural young actor, lucky you. But if that’s not the case, you can employ a few simple techniques to help even a beginner deliver the goods. The following four-and-a-half-minute tutorial from Film Jams provides sensible, easy-to-execute strategies. For example, as an antidote to wiggling, have the young performer stand in a large pot. The confinement makes “staying on the mark” automatic.