"Ministry" is from the Greek word diakoneo, meaning "to serve." In the New Testament, ministry 
is seen as service to God and to other people in His name.  Jesus provided the pattern for Christian ministry - He came, not to receive service, but to give it.

The Christian should minister by meeting people's needs with love and humility on Christ's behalf.  We are to minister to others out of our devotion to Christ and our love for others, whether the other people are believers or non-believers.  Ministry to others should be impartial and unconditional, always seeking to help others as Jesus would.

The content of ministry seems to prioritize the ministering in spiritual things, not just practical things.  Ministry should certainly place emphasis on sharing the Gospel of Jesus Christ with others so they can come to know Him and receive Him as their Savior, go on to experience Him as Lord of their life, and go even further to know Christ as the essence of their life.  Ministry can, and should, include ministering to the physical, emotional, mental, vocational, and financial needs of others.

Each Christian should be in the ministry of helping people.