How do we know someone is spiritual? How do we know what we are about to read is going to build our spiritual life? There are spiritual cues.
Does that writer believe certain basic Biblical principles? The first thing to look for is does the writer believe in what is termed our being tripartite. If they know nothing of our spirit's different functions from the functions of the soul, then you know that person is at a serious disadvantage in disclosing truth in his life, and can be of little benefit to you.
Next, what to look for is does the person believe in what is called osas arminian. The easy way to nullify for consideration of a writer is to know whether they are calvinist or non-calvinist. After knowing they are not calvinists, you would be implored to ask by the Holy Spirit do they believe new birth can never be lost? If so, they accept osas arminian.
What's next? Here we go deeper to discern the consideration put further to seek true depth, sincerity and honesty towards God's loving Word. Does the person believe in gap restoration? In other words, do they believe that God made the earth desolate in Gen. 1.2 because of fallen Lucifer's sinning over the cities of the demons in earth's earliest ages? And then follows the restoration of creation in a long period summarized by the six summary literal 24 hour days.
If the writer has passed this test, there is yet 2 vital elements to underscore whether you have come upon a deeply spiritual Christian. Does the writer accept partial or separate rapture? In other words, do they believe that the first rapture is according to readiness of just those Christians who are accounted worthy for keeping the Word of His patience (Rev. 3.10, Luke 21.36). Though saved, the non-overcomers must pass through the Tribulation either to be martyred or remain "alive" and "left" (1 Thess. 4.15-17; Matt. 24.37-40-41).
Lastly, and this will be the most difficult to accept after passing through the chain of truth disclosed in the above 4 points, does the believer accept Biblical locality in which Apostles appoint Elders to to take care of cities: biblical localities or church locales.
Ancillary tests are also worth considering: do they accept women elders as well as women apostles? Do they believe tongues are languages? And to reach even more depth, do they accept the numerous truths in the questions asked at registration to Biblocality Forums and in Edit Profile.
This is the test. May I say forthrightly, the most spiritual is Watchman Nee. None compare to his accuracy in the dispensation of grace subsequent to the ratification of the 66 books of God's Word. If you are aware of this and able to discern these truths we can begin to unfold to the Church what is most precious for strength and vitality to achieve what God is waiting for the Church to accomplish.
Praise the Lord!