4. They act happy.
In the realm of religion, theological brilliance rarely comes close to a happy personality in its ability to attract (healthy) people to a given faith. The best arguments for a religion are that its adherents are better (more moral, more deep) and happier human beings as a result of their commitment to that religion.
In light of that, the happiness that the vast majority of Chabad rabbis and their wives radiate is perhaps the most powerful asset in the Chabad rabbi’s arsenal. That they maintain this cheerful demeanor (and I have been with dozens of Chabad rabbis away from their public roles), given their often-difficult financial and social situations (not to mention normal human problems), is a credit to them — and to their faith. This is very attractive to the overwhelmingly non-Orthodox Jews with whom they relate.
Lesson: Nothing is more powerful than a happy demeanor in attracting people — to one’s faith or to one’s self (singles take note).
5. They act nonjudgmental.
Finally, I have come to believe — after initial skepticism given the level of Orthodoxy within Chabad — that they mean it when they say they love all Jews regardless of their level of halachic observance. My own experience had led me to believe that most Orthodox Jews do judge other Jews — consciously or not — by their level of observance. And Chabad takes some flak for this from some other Orthodox Jews. For example, few other “black hat” (“ultra-Orthodox”) Jews are as welcoming to Jews who drive on Shabbat to be with them as the Chabad rabbis.
Lesson: If Orthodox Jews judged fellow Jews solely by their ethical behavior and not by their ritual behavior, both Orthodoxy and Jewry would be much better off.