From John Piper:
I have in mind at least five things—five ways to make God known through your secular job and all of them are important. When one of them is missing, the witness to the truth of Christ suffers.
1. The excellence of the products or services you render in your job shows the excellence and greatness of God.
2. The standards of integrity you follow at your job show the integrity and holiness of God.
3. The love you show to people in your job shows the love of God.
4. The stewardship of the money you make from your job shows the value of God compared to other things.
5. The verbal testimony you give to the reality of Christ shows the doorway to all these things in your life and their possibility in the lives of others.