Jehovah's Witnesses are a fundamentalist Christian denomination best known for door-to-door evangelism, distribution of religious literature such as The Watchtower and Awake! magazines, and their refusal to accept blood transfusions.
The religion's organization report over 7,000,000 members worldwide, and over 18,000,000 attendees at their annual Memorial ceremony.  Third-party reports estimate the number to be 30-60% higher than reported by the religion.
Jehovah's Witnesses use their own translation of the Bible, the New World Translation of the Holy Scriptures, first published in 1961. This was followed by a revised 2013 version which includes an introductory 20 question and answer section, outline of contents before each book and two appendixes (A and B) with biblical information, teachings doctrines of the Jehovah's Witnesses.
God and Jesus
Jesus is the Archangel Michael and not God.  They reject the concept of the Trinity.  They believe that Jesus died on a stake, not a cross and in any cause this symbol should not be used in worship.  They believe the resurrection of Jesus was spiritual, not bodily. 
Prophecy and the end of the world
Jehovah's Witnesses have proclaimed numerous dates for the Apocalypse, principally 1914, 1925, 1975, but also 1799, 1874, 1878 and 1918. They have passed without apparent incident. New doctrines were added as the predictions failed, usually by convenient reinterpretation of scriptures.
Jehovah’s Witnesses believe that only 144,000 people will go to Heaven.  They generally believe that since 1935, no one can go to heaven because there have already been 144,000 within their denomination; in other words Heaven is full. Teachings were revised so that more recent faithful believers will spend an eternity on Earth instead.
- "Hence, especially after 1966 it was believed that the heavenly call ceased in 1935. [...] On the other hand, as time has gone by, some Christians baptized after 1935 have had witness borne to them that they have the heavenly hope. (Romans 8:16-17 ) Thus, it appears that we cannot set a specific date for when the calling of Christians to the heavenly hope ends. "
People in Hell are thought to be in an unconscious state, similar to death. 
Witnesses are discouraged from voting in elections and generally remain neutral on politics.  Also, Witnesses refuse to serve in the military.  Smoking and gambling are not tolerated and can lead to dis-fellowship. 
One of the most visible aspects of Jehovah's Witnesses is their door to door preaching. This is referred to as "field service". Field service also includes telephone contact, letter writing and street witnessing.  It is a central activity of the denomination  and is required of believers unless circumstances prevent it. There has been a recent move toward street witnessing in parts of the US and UK, which is a boon to believers that dislike door to door preaching. 
- "For the Jehovah's Witnesses (JWS), the door-to-door ministry appears to be more of a demonstration of faith and solidarity, than a real effort to convert. I grew up in the Jehovah's Witness religion (or cult, as I prefer to think of it), and the dedication to the preaching work promotes a shared feeling of persecution and self-righteousness. "
Jehovah's Witnesses believe that blood is a sacred representation of life and that God forbids its use for purposes other than atonement for sin (sacrifice). Believers are forbidden from eating meat from which the blood has not been drained, food products containing blood, and from receiving blood transfusions, regardless of its medical necessity and of the consequences to their life or health.
Specifically, they are directly forbidden from willingly accepting a transfusion of stored whole blood, red blood cells, white blood cells, platelets, and plasma, on penalty of disfellowshipment and the threat of God's disfavor. Preoperative extraction followed by postoperative re-transfusion of their own blood is also disallowed, though certain intraoperative re-transfusion procedures (such as salvage) are allowed. Organ and bone marrow transplants are discouraged as well, though the final decision is left to the individual. Those choosing to follow discouraged actions are often informally ostracized. They are directed to follow their own personal conscience in deciding to use other components of blood, or other products derived from or produced in blood (such as antivenins).
One of the controversial aspects of their refusal to accept blood transfusions is in that, against the advice of their doctors and surgeons, they often hold their critically ill minor children to the same rule, who are themselves not mature enough to decide to follow the belief willfully. This is an instance of religiously motivated medical neglect.
It is difficult to assess actual membership among Jehovah's Witnesses, as their organizing body reports neither officiated members nor church attendance. Instead, they report:
- The peak number of members who submit a report on their evangelism efforts, tabulated monthly.
- Combined attendance at their annual memorial ceremony.
- Combined peak attendance at their annual three-day convention.
The latter two do not reflect membership, as attendance of both includes casual visitors, one-time visitors, and unbaptized children of Jehovah's Witnesses who attend with their parents. Ministry campaigns are carried out for a few weeks before the event in an attempt to invite as many new people as possible.
The first is not an exact representation of actual membership, as it excludes those who attend services, consider themselves members, but who do not participate in evangelism efforts. It excludes even officiated members who do not evangelize. But given that better information is not reported, it may be considered the best representation available.
In reporting religious affiliation, government censuses, pew surveys, and statistical abstracts usually rely on self-identification. As such, they include children and others not recognized as members by the church, and thus find the number of Witnesses to be 30-60% higher than reported by the religion itself. But as they are collected the same way regardless of religion, these reports may be considered accurate for comparing one religion to another.
The practice of "disfellowshipping", more commonly known as excommunication or shunning, is used by Jehovah's Witnesses to punish those who break the rules of the religion and fail to convince congregation elders that they have repented. Church members are prohibited with associating with disfellowshipped people, and in many situations even members of their immediate family. An exception can be made where regularly speaking with the disfellowshipped person cannot be avoided, such as between married couples, for the care of children, and for business contracts and partnerships. Continuing to associate with a disfellowshipped person is itself a basis for disfellowshipping, though this is rarely the actual penalty. In the case of a family member, one would more likely be excluded from leadership positions and certain church activities.
- "If, however, a baptized Witness makes a practice of breaking the Bible’s moral code and does not repent, he or she will be shunned or disfellowshipped. "
Those who renounce their membership with the church are "disassociated." This is basically equivalent to disfellowshipping, except that it is not due to breaking any rules, and is initiated by the member himself.
Disassociation occurs when a person specifically renounces his membership, either by formally informing the congregation elders of his/her decision or by participating in the services/rituals of another Christian denomination or non-Christian religion.
Most holidays are of either religious or political origin, which Witnesses consider idolatrous worship of either a false god or the state, respectively. Thus, Jehovah's Witnesses do not observe any secular or religious holidays or celebrations, save wedding anniversaries.
Jehovah's Witnesses also have one religious celebration they do observe: the memorial of Christ's death.
The memorial of Christ's death, known as "The Memorial", is the only celebration officially endorsed by the church and observed by followers. This celebration is their version of the Last Supper.
Their practice of it involves a scripted sermon about the significance of Christ's sacrificing himself, and the importance of carrying on the tradition. This sermon is almost identical every year. It concludes with wine and unleavened bread being passed around the audience. Most members (99.9%) simply pass the bread and wine on to the person sitting beside them, but a few who feel they are anointed by God to act as rulers eat and drink them.
Birthdays are viewed as a form of idolatry, and the common American custom (getting really drunk at your friends' expense, which is great) contrary to scriptural principles. The celebration of birthdays is therefore expressly disallowed.
However, what a celebration consists of is not explicitly defined by the Jehovah's Witness organization. Some members do celebrate birthdays surreptitiously.
Christmas is considered by Witnesses to be a celebration of mostly pagan origin (which is largely true), observed on a date and in a way that coincides with (and they believe is rooted in) several pagan rituals. They do not celebrate Christmas and generally consider it one of the more abhorrent holidays.
It is perfectly acceptable for Witnesses to celebrate wedding anniversaries. The idolatrous aspects of admiring and giving gifts to someone on the yearly anniversary of their birth do not apply to admiring and giving gifts to a married couple on the yearly anniversary of their wedding.
A cult is popularly defined as an individual or organization which employs intensive methods to control behavior, thinking, and emotions of its followers. Jehovah's Witness religion requires members to isolate themselves from social interactions outside the religion. Those who do not do not follow their rules are disfellowshiped. This causes an almost total collapse of that person's social support structure. Witnesses' lives are tightly controlled by their church. They are also discouraged from researching their religion or developing critical thinking skills. 
"If we get to thinking that we know better than the organization, we should ask ourselves: “Where did we learn Bible truth in the first place? Would we know the way of the truth if it had not been for guidance from the organization? Really, can we get along without the direction of God’s organization?” No, we cannot!"
- — Watchtower 1983 January 15 page 27 – “Fight Against Independent Thinking”.
"Approved association with Jehovah’s Witnesses requires accepting the entire range of the true teachings of the Bible, including those Scriptural beliefs that are unique to Jehovah’s Witnesses."
- — Watchtower 1986 April 1 page 30-31 – “Questions From Readers”.
During the early 20th century, Jehovah’s Witnesses saw black people as inferior. Black people it was believed had the curse of Ham in their hearts and were fit to be servants. Black people could get spiritual benefits by staying meek and accepting their inferior status. Black people were not encouraged to feel good about being black, rather they should hope to become white. As a special blessing black Jehovah’s Witnesses might become white through God’s intervention. Black people were uneducated and therefore would not benefit from the tracts and reading material supplied to white congregations.
Prejudice is much less evident in the 21st century, though few black people have reached the highest administrative levels of the church. 
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- ↑ When Was Ancient Jerusalem Destroyed?—Part One, w11 10/1 pp. 26-31, The Watchtower (2011)
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- ↑ Gathering Things in Heaven and Things on Earth, w06 2/15 pp. 21-25, The Watchtower (2006)
- ↑ Questions From Readers, w07 5/1 pp. 30-31, The Watchtower (2007)
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- JW Victims, Documents the harm to individual believers
- JWfacts Criticism of Jehovah's Witnesses
- The beliefs of Jehovah's Witnesses and how they differ from mainstream Christianity.
- Jehovah's Witnesses at a glance
- Jehovah's Witnesses official website
- Jehovah's Witness Recovery, support forum for those leaving or who have left.