put one's best foot forward

Example: “It's your first day, so put your best foot forward.”

Origin: In English by the late 1500s: Shakespeare has "the better foot before" in King John (1595), using the grammatically stricter comparative rather than the superlative, since only two feet are being compared. Sir Thomas Overbury's 1613 poem "A Wife" gives the version that eventually won out, "he is still setting the best foot forward." One folk explanation ties the phrase to an old superstition that the left foot was unlucky, making the "best" foot the right one to lead with quite literally — though like much foot-superstition lore, it isn't documented as the phrase's actual source, only as a belief that existed alongside it.