事奉神，服侍（服事） 人。
A. δουλεύω (service - Ephesians 6:7) vs. B. διακονέω (minister - Mark 10:45)
Some consider the two similar. If A. then B. must be true.
I would point out that vice versa is not true.
As for serving God, the term δουλεύω is connected with slave. Which is why Paul used "I'm a slave of Christ, etc.".
In many churches today, specifically Chinese Immigrant churches, in my own experience, I have seen many church members love to use all kinds of works in church as "Serving God".
I see a problem in their understanding of it. This misunderstanding, is perhaps due to the improper motive they would have behind "serving God". They often use this phrase to insist everyone in the church to do something at church, or else, they would not be "serving God".
To counter that, I shall point out that listening to sermons is also considered "Serving God". This means, that everyone who attends church is already serving God. Therefore, as I had mentioned before, there's no such thing as "consumer Christian", another phrase churches love to use to make congregants do church works.
Now, due to this wicked motive and serious misunderstanding of "serving God". There could be two kinds of serving God that can be good (The bad kind of serving God would be to serve God passively or negatively such as the slothful servant who hid his master's talent, Satan, Judas Iscariot, etc.):
1. Serving God alone. (This also may sometimes look like serving with fellow church members or in agreement with church members that one is serving God, but due to their misunderstanding in the doctrine of servitude, one is said to be serving God alone).
2. Serving God with the fellowship of the Saints.
So, when I go and help a non-Gospel Centered church like CCCNY in teaching their Sunday School, I am serving God. But I am serving God alone. If I do the same at Redeemer, it is likely the 2nd kind of serving God, which could be more joyful.