The Church officers mentioned in the New Testament which this church has maintained include those of:

• Presbyters (ministers of the Word and Sacrament also called pastors) - Responsible for teaching, preaching, baptisms, pastoral care, leadership, management, ...
• Elders - Generally responsible for internal affairs. They make up the Session of the Church which is responsible for governing the church.
• Deacons - Generally responsible for external affairs. They represent the caring side of the church and seek to minister either within or beyond the community of faith. They also dispense the sacraments.

Officers must be ordained, which is usually a short ceremony where they answer questions about belief and duties. They are then confirmed by a laying on of hands by other officers. In the Catholic Church confirmation of ordained officers is a Sacrament.

Minister:
The pastor is responsible for studying, teaching, and preaching the Word, for administering Baptism and the Lord's Supper, for praying with and for the congregation. With the elders, the pastor is to encourage the people in the worship and service of God; to equip and enable them for their tasks within the church and their mission in the world; to exercise pastoral care, devoting special attention to the poor, the sick, the troubled, and the dying; to participate in governing responsibilities, including leadership of the congregation in implementing the principles of participation and inclusiveness in the decision making of the church, and its task of reaching out in concern and service to the life of the human community as a whole. With the deacons the pastor is to share in the ministries of compassion, witness, and service. In addition to these pastoral duties, he or she is responsible for sharing in the ministry of the church in the governing bodies above the session and in ecumenical relationships. The pastor is the Moderator of session.

Ministers may be designated as educators, chaplains, pastoral counselors, campus ministers, missionaries, partners in mission, evangelists, administrators, social workers, consultants, or in other specific tasks appropriate to the ministry of the church.

Elder:
Elders should be persons of faith, dedication, and good judgment. Their manner of life should be a demonstration of the Christian gospel, both within the church and in the world.

Elders exercise leadership, government, and discipline and have responsibilities for the life of a particular church as well as the church at large, including ecumenical relationships. They shall serve faithfully as members of the session.

It is the duty of elders, individually and jointly, to strengthen and nurture the faith and life of the congregation committed to their charge. Together with the pastor, they should encourage the people in the worship and service of God, equip and renew them for their tasks within the church and for their mission in the world, visit and comfort and care for the people, with special attention to the poor, the sick, the lonely, and those who are oppressed. They should inform the pastor and session of those persons and structures which may need special attention. They should assist in worship.

They should cultivate their ability to teach the Bible and may be authorized to supply places which are without the regular ministry of the Word and Sacrament.
1 Peter 5:1-5

Deacon:
Ministry and Gifts:
The board of deacons is composed of persons of spiritual character, honest repute, of exemplary lives, brotherly and sisterly love, warmth, sympathies, sound judgment and general good character.
1 Timothy 3:8-13

The deacons motto is: "Sharing Christ's love".
They administer the welfare matters of the congregation.

Responsibilities:
Deacons exemplify the caring side of the church and seek to minister either within or beyond the community of faith to:

• The needy
• The sick
• The friendless and
• The distressed

The office of deacon as set forth in Scripture is one of compassion, witness, and service after the example of Jesus Christ. They also assume other duties that may be delegated to them from time to time by session, such as leading the people in worship through prayers of intercession, reading the Scriptures, presenting the gifts of the people, and assisting with the Lord's Supper.

They may be individually commissioned by the session to particular tasks consistent with the responsibility of their office.

Our 1,100 member church has 16 deacons who serve 3 year terms.

See also:
The Biblical Role of Deacons at BaptistStart.com
Westminster Presbyterian Church -- Deacons
Acts 6:1-7
Philippians 1:1

The Board of Trustees is responsible of the acquisition, maintenance and disposition of the property of the church and management of any permanent special funds for the furtherance of the purposes of the church. They have rolls including, steward, proprietor, financier, caretaker, enabler of ministry and manager.
Qualifications are similar to those of deacons.

Source: The above is based on the Presbyterian Church (U.S.A.)
  - Book of Order G-6.000 - Form of Government.
Other protestant denominations have similar boards.

Links:
Presbyterian polity - Wikipedia
Pastor, Elders and Deacons ta the Reformed Churches in the US.