The Ephod was inscribed with the names of the 12 tribes of Israel to remind God of the tribes whom he had made a covenant, as long as the priest bore the names of Israel on his shoulders the Lord would not forget to be gracious to Israel.
The Breastplate was also used as a function of remembrance, it contained the 12 tribes of Israel as well, in addition it is called the Breastplate of Judgement, it contained the sacred lot, the Urim and Thummim, worn above Aaron’s heart it would remind Aaron and God that justice originates with God and is maintained by God.
The Mitre was placed on the forehead of the High Priest it was inscribed with the words Holiness to the Lord. The Mitre was on Aaron’s head continually so that the children of Israel would be acceptable to the Lord. It was a reminder of consecration and the importance of approaching the Lord in Holiness.