I believe in believers' baptism by immersion though being inter- denominational, I do not deal with the individual texts that BCC raise without my understanding and hermeneutic being taught simultaneously. I'll do this on a one to one, if I tell the student beforehand that we are diverse on non-essentials as per the neat little IVP booklet on Baptism. You may find that booklet helpful.
A more Sociological Perspective on those "christian" (note the quotations) cults:
1. "Pet" doctrines or teachings. (and they won't be justification by faith or the gospel, rather it will be baptism, gifts, apostleship, blood, godhood, etc).What to say to those who ARE involved.
2. Relationship with other denominations, ministries. (NOT. either they are exclusivistic, or paternalistic).
3. Approach to the member's extended families. (Not seen as emotional health but as potential convert/functionaries only. Minimal contact allowed or ever encouraged).
4. Approach to (spiritual) guidance. (NOT private prayer, but rather through new revelation(s), or through leadership or your sheppherd/discipler. Teachable means you can only receive teaching through one primary person in a chain of "authority")
5. Implementation of "accountability." (disciple is not making disciples of Jesus, but rather of ________. Discipling = control. Time in group events = spirituality. Money is heavy handedly controlled via guilt, and a storehouse in the "in" group only mentallity)
6. Relationships of the (leader, discipler, shepherd) to the Led. (Often co-dependant. NT disciples were "of the Lord" except for the use in Acts 9:5 only, and this is not a clear commendation, but in these groups, the fullest sense of co-dependancy takes shape in these relationships. Both need each other to acheive spirituality/group approval.)
7. Double standards. (Commands and exhortations are given by apostles to followers but are not maintained among leadership, this is especially true regarding the use of free time, $$, and access to free thought and reading/study materials).
8. Disciple Abuse and the Relationship to former members. (ostracism, and ...)
9. The use of Shaming and Anger. (Public knowledge of private confidences. Sin confessing is explicit and allegedly confidential until someone is seeking to leave the group, then "it could be that such and such and such and such are affecting your judgment and so I feel I'll need to share these with your entire circle of friends as a prayer request, IF you do not stop doubting (God), the group).
10. Rationalizing crisis and Confusion. (There will come times of increasing rationalization that reaches crisis proportions and confusion that the group is not meeting all the needs it is suppose to be able to meet. Though this expectation is unrealistic, that is not consciously realized).
1. Do not persecute as this can entrench. Do not debate too quickly as you may not really know the level of their entrenchedness.Hope this helps.
2. Affirm their search for God, eternal life, truth, purpose, authority, community...
3. Assess beliefs concerning; Jesus (all of #2 above), and note the level of conviction for each belief.
4. Assess the intensity of assimulation into the pressure groups' community. Do they have ANY other close friends they trust.
5. Invite to an EBS, IBS, or 1:1 with you. Do not do a 2 on one you thing with their discipler unless you are strong psychologically, and biblically. Generally I'd advise against it.
6. Stay centered on Jesus, the Cross, Empty tomb, faith.
7. Study. Do not fear thinking and do not fear the truth.
8. Confront dehumanization of the person (your friend), via socio-structures seen on earlier overhead. The puppet syndrone of disciplers, apostles, organizations, and the lack of independant critical thought.
9. Confront exclusivities, be they for the "true" group or the "most spiritual" group.
10. Introduce to former members who have been freed carefully, and in a progression of interventions as outlined above. Introduce to other strong Christians who are aware of these principles, but do not introduce them to new, less stable Christians because they and their discipler are quite edept at "sheep stealing", and harm can result.