Make every effort to keep the unity of the Spirit through the bond of peace. There is one body and one Spirit, just as you were called to one hope when you were called; one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all. Ephesians 4:3-6 (NIV)
We have been called to live and walk towards one common purpose of a one God from whom we all came, in whom we all exist and for whom we all live. Our one common purpose is to let God express Himself in and through each and every one of us. This is how we achieve unity.
Because the one and same God is in us we can live and function as one body. Just like the human body is made up of many parts with different functions yet operates as one, we have been called to operate in our various walks and callings as one. We are not to compare with or compete against each other. We are to complement and complete each other. This is the attitude of unity. Not necessarily doing the same things but in our various departments working towards the same aim of mutual and collective up building.