Look for Uruks with green icons over their heads. Interrogating them reveals the identities, locations, and—most importantly—the Weaknesses and Strengths of Captains.
To get the best gear, let a Captain kill you. This increases their power level. If you then exploit their specific weakness and issue a , you have a very high chance of looting an Epic Rune upon their death. Middle Earth: Shadow of Mordor Complete Edition
If a Captain has a "Fear of Caragors" or "Fear of Burning," use it. Scaring a Captain makes them break rank, allowing for an easy finish. Look for Uruks with green icons over their heads