This is from the WTS website: http://www.watchtower.org/library/jt/index.htm?article=article_08.htm#preach
If I become one of Jehovah's Witnesses, would I be expected to preach as they do?
When one becomes filled with the knowledge of the promised earthly Paradise under Christ's Kingdom, one wants to share it with others. You will too. It is good news!? Acts 5:41, 42 .
Doing this is an important way of showing that you are a disciple of Jesus Christ. In the Bible, Jesus is called "the faithful and true witness." When on earth he preached, saying: "The kingdom of the heavens has drawn near," and he sent out his disciples to do the same. ( Revelation 3:14 ; Matthew 4:17 ; 10:7 ) Later, Jesus commanded his followers: "Go therefore and make disciples of people of all the nations, . . . teaching them." He also foretold that before the end, "this good news of the kingdom will be preached in all the inhabited earth for a witness to all the nations."? Matthew 24:14 ; 28:19, 20 .
There are many ways of declaring this good news. Conversation with friends and acquaintances often opens the way to do so. Some do it by writing letters or by using the telephone. Others mail literature containing material that they think an acquaintance would be especially interested in. Out of a desire to miss no one, Witnesses go from door to door with the message.
The Bible contains this warm invitation: "The spirit and the bride keep on saying: 'Come!' And let anyone hearing say: 'Come!' And let anyone thirsting come; let anyone that wishes take life's water free." ( Revelation 22:17 ) Telling others about the Paradise earth and its blessings is to be done willingly, out of a heart filled with a desire to share this good news.
We are sure that you have other questions about Jehovah's Witnesses and their beliefs. Perhaps some issues are controversial in nature. We would like to answer your questions. Space is limited in this brochure, so we invite you to ask the Witnesses locally. You can do so either at their Kingdom Hall meetings or when they visit you in your home. Or you may send your questions to Watch Tower, using the appropriate address.