Tell them to go into it with their eyes open! IF they are a religious person in anyway shape or form this is not an easy path......
My wife was born in to the "truth" and whilst she is definitely not a hard core dub as she drinks, gambles, has tattoos, sex before marriage, celebrates birthdays, christmas gives to non dub charities.....she is still a dub
Firstly I love her to bits, she is my best friend
However, the dub thinking can drive you nuts at times, dealing with other dubs (or in our case total avoidance) can be entertaining, the die hard dub relatives (mother in law in my case) biblical preaching that she want me to be saved as well!
An then of course you will have to go to memorial to waste 45 minutes listening to the used car salesman routine slam every other religion, promise the end is comming soon and watch 150 people pass a glass of wine and crackers around!
All these bits will put you to the point where you will snap eventually and blast someone (most likely your wife) with your thoughts over the WBTS!
A then the serious dub mentality kicks in! As many here will tell you, and from personal experience, any open attack on the organisation to them is like persecution, in addition you have hit at what they see as a core attribute of what them and you might have well said you hate them! You don't but thats what it feels like to them as they have been "brainwashed" to think that way and then if you are lucky you might be allowed to sleep on the couch!
Only your friend can make the choice but make sure he is aware of what lies in wait for him if he makes the leap!