"The altar is 'the center of thanksgiving that the Eucharist accomplishes'" (n. 56 Built of Living Stones). "During the Liturgy of the Eucharist, the altar must be visible from all parts of the church, but not so elevated that it causes visual or symbolic division from the liturgical assembly." (n. 59 Built of Living Stones)
Only what is required for the celebration of the Mass may be placed on the mensa of the altar; namely, from the beginning of the celebration until the proclamation of the Gospel, the Book of the Gospels; then from the presentation of the Gifts until the purification of the vessels, the chalice with the paten, a ciborium, if necessary, and finally the corporal and the pall and the Missal. (n 306 GIRM)
Once Mass is complete, the Altar is to be BARE...do not leave the missal and clothes (especially the corporal) on the altar.
The central focus of the areas in which the word of God is proclaimed during the liturgy is the ambo. The design of the ambo and its prominent placement reflects the dignity and nobility of that saving word and draws the attention of those present to the proclamation of the word.(n 61. Built of Living Stones)
"The chair of the priest celebrant stands as 'symbol of his [office] of presiding over the assembly and of directing prayer.'...The chair reflects the dignity of the one who leads the community in the person of Christ, but it never intended to be remote or grandiose. (n 63. Built of Living Stones)
"The [most appropriate] place for the chair is the head of the sanctuary and turned toward the people" (n 64. Built of Living Stone)