Q - In what ways does Christian writing differ from nonChristian writing? Stated differently, what one element are publishers of Christian material most concerned about.
A - I would have to start by saying that it does vary from publisher to publisher. Generally speaking, christian publishers want there to be some sort of a Christian emphasis or slant to the piece of writing. However, the degree is what varies. Some publishers want an explicit Christian message--meaning there is no doubt that the focus is Christian. Even with those, there are few that would expect you to go so far as to include the plan of salvation.
At the other end of the spectrum are those that will accept an implicit Christian message--meaning it might only be inspirational or character building (if for children or teens). The important thing for you to know is where a particular publication falls on that line, and be sure your emphasis matches. You can usually determine that by reading both their guidelines and one or more sample copies. Your chances of selling to a particular publication will increase greatly if you understand where they are coming from.