A literary foil is someone who highlights another character's trait, usually by contrast. The scriptures are full of these character foils. Examples include God/Christ v Satan, Cain v Abel, or Nephi and Sam v Laman and Lemuel. Often times a chapter or story will highlight events in two different people or groups of people. This is done on purpose and oftentimes there are direct differences that were meant to be discovered and noted by the reader to gain more meaning.
Look For: Look for two people or groups that seem opposites of each other. Then notice the specific differences and compare them to each other.
Example: Numbers 14 Caleb vs. Children of Israel. Compare how Caleb acted to how the Children of Israel acted when they were first going to enter the promise land. For example, the children of Israel murmur, but Caleb has another spirit--which means he had a different spirit than the rest of the children of Israel (v. 24). The children of Israel want another captain (v. 4), but Caleb remains the Lord's servant (v. 24). In the end, Caleb gets to go to the promised land while the children of Israel will suffer and die in the wilderness. Finding these comparisons can help us see what the end result of each direction is and determine what types of lives we wish to live.
Example: Isaiah 14:12-23 The Foil is in the comparison between what Lucifer wants (v. 13-14) and what he will receive (vv. 12, 15-23). Notice how perfectly correlated they are with each other. For example, Satan wants to "ascend into heaven" (v.13) but he will "fall from Heaven." Satan wants to "sit upon the mount of the congregation, in the sides of the north" but he will "be brought down to hell, to the sides of the pit" etc. What this shows is that if we don't put God first in our lives and trust in anything but Him, no matter what we desire, it will turn to the opposite.
(Adapted from Panning for Gold: Various Methods to Understand and Apply the Scriptures to Ourselves by Eric Bacon, Northwest Area Seminaries)