They tend to take a very literal interpretation on the Bible, though they've excised more than the KJV. Believing that there are exactly 144,000 elite that will be taken up into heaven, they constantly struggle to be able to join this super-friends list. Converting a non-beliver grants them a certain amount of points and they are tireless workers, where every member is a proselytizing missionary. They gain more points if they manage to convert fellow Christians to their cause; the most points are earned for converting members of other religions that also proselytize (i.e., Mormons).
They hand out pamphlets everywhere, namely The Watchtower, with detailed views of the bounty that awaits the believers in heaven (gourds filled with all kinds of foods, multi-cultured peoples bedecked in ceremonial robes) and the hell that awaits the non-believers (20-ft devils with cloven hooves, wielding whips and chains and murals of fiery torment).
They usually know their scriptures quite well, but are genuinely at a loss if a fellow Christian quotes a passage (out of a common Bible) that happens to not be in their revised version. They seem affable, albeit hiding deep ulterior motives--you're just a number they're hoping to cash to gain entry to the elite 144k.