The Greek word translated "minister" is diakonos, which is sometimes translated "deacon." It is most frequently rendered either "minister" or "servant."
Every Christian has received some gift in trust from God to be held and used for the benefit of the whole church. The gifts may vary widely, but the ministry or the service of each is to be according to the character of the gift. As in Paul's body analogy, the finger does not do the same job as the toe, but the fingers are a gift to the body so that the body can function. However, the toes are also a gift to the body so it can function better in another area. It contributes its part to the well being of the body, but it does not have the same characteristics as a finger does—or the nose, ears, eyes, or mouth.
Everybody has been given gifts by God, and He has given them to the person so that he can serve the Body, allowing the Body to function better than it would have otherwise if it did not have that part, or that gift.
We are to do this as a steward, and above all things, a steward must be faithful. One cannot be faithful unless he has faith. This is where faithfulness begins—with faith, with a belief. Then we carry through. As we minister the gift to the Body of Christ, we become faithful—reliable, trustworthy, responsible—in carrying it out. Thus, each Christian is responsible to follow through faithfully in his service to the brethren.
William Barclay's translation of I Peter 4:10 reads:
As each has received a gift from God, so let all use such gifts in the service of one another, like good stewards of the grace of God.
A good steward is a faithful steward. A good steward, or a good servant, is one who follows through with his responsibility. Being a faithful steward of God's gifts can at least appear to be a discouraging responsibility, given our knowledge of how weak we are, but we will never be faithful if our beliefs are or remain mere preferences. We must be convicted of the rightness of what we believe, or we will never be faithful.