I've looked, and come to pretty well the same conclusion that Auld Soul has. Whereas Orthodox Christianity has a brief declaration of beliefs (You believe it, you're a Chrisitian. You don't, you aren't) that nearly all denominations ascribe to, the JW's are expected to believe EVERYTHING that comes out of the mouth of the "Faithful and Discreet Slave". http://www.creeds.net/ancient/nicene.htm
AlanF maintains that the only key doctrine of the Jehovah's Witnesses is, "Follow the Faithful and Discreet Slave." He argues that if the Watchtower magazine declared that the moon was made of green cheese, the JW's would be obliged to believe it. If the Watchtower approved blood transfusions, the JW's would then agree that blood transfusions are OK.
I think the closest thing we have to "core doctrine" for the Jehovah's Witnesses is the 104 questions at Baptism, listed in the back of the "Organized to do Jehovah's Will" book.
Part 1, Elementary Bible Teachings (35 questions) Part 2, Jehovah's Righteous Requirements (37 questions) Part 3, Jehovah's Arrangement of Things (32 questions)
Here are my favorite gems:
Part 1, Q 20 Who is Satan the Devil? Where did he and his demons come from?
Part 2, Q 2 What is the only Scriptural basis for divorce that frees one to remarry?
Part 2, Q 7 How does Jehovah view (a) the unlawful shedding of human blood? (b) abortion? (c) suicide?
Part 2, Q 8 What responsibility rests upon a person who is infected with a communicable disease that is potentially fatal?
Part 2 Q 9 To avoid transmitting an infectious or a potentially fatal disease to others, why should an infected person (a) not initiate public displays of affection such as hugging and kissing? (b) attend the Congregation Book Study at the Kingdom Hall if at all possible? (c) not react negatively when some choose not to invite them in to their homes? (d) Why should a person who may have been exposed to an infectious disease voluntarily choose to have a blood test before beginning a courtship? (e) Why should one having a communicable disease inform the presiding overseer before getting baptized?
Part 2 Q 13 How should Christians view the shortcomings of fellow believers?
Part 2 Q 20 Why should Christians abstain from all nonmedical use of addictive or mind-altering natural or synthetic substances?
Part 2 Q 29 What is the Christian's position as to the world alienated from God?
(Answer: They are no part of the world, just as I am no part of the world. - John 17:16.
Do you not know that the friendship with the world is enmity with God? Whoever, therefore, wants to be a friend of the world is constituting himself an enemy of God. - Jas. 4:4.)
Part 2 Q 31 When a person separates himself from the world and becomes a Christian, what treatment should he expect from those in the world?
(Quotes John 15:19, 20; 2 Tim. 3:12; 1 Pet. 4:4)
Part 2 Q 34 Would it be proper for true Christians to share in worship with other religious groups?
(Quotes Rev. 18:4, 5; Matt. 7:13, 14, 21-23; 1 Cor. 10:30; 2 Cor. 6:14-18)
Part 2 Q 36 How can you determine whether you should observe or participate in celebrations that are popular in your community?
(Quotes John 17:16; 1 Cor. 10:21; Ps. 106:35; 1
Pet. 4:3)
Part 3 Q 3 Is the wife whose husband is not a believer freed from his headship?
(Quotes 1 Pet. 3:1, 2)
Part 3: Q 13 What is the Governing Body of the Christian congregation?
(Quotes Acts 15:1, 2)
Part 3: Q 15 How do members of the congregation demonstrate submission to the headship of Christ in the congregation?
(Quotes Heb. 13:7; Heb: 13:17)
Part 3: Q 25 What should be our attitude toward giving of ourselves and of our material possessions in Jehovah's service?
(Quotes 1 Chron. 29:14; 2 Cor. 9:7)
Part 3: Q 26 What attitude should we have when we are persecuted or undergoing trial?
(Quotes Matt. 5:10-12; Jas. 1:2, 3; Acts 5:41)