Hi Luca,
I can't answer most of these questions. There are too many variables at play. If you give me something specific, I have a better chance of giving a thoughtful answer.
In several communities I've been with, I've greeted new members manually, not using automated methods. In one of my communities, new member engagement increased from 35% to 65% within six months. Other communities haven't had that dramatic effect, but, in general, it's a good tactic.
Does anyone in this forum have some sort of training manual / tips & tricks to engage internal teams participating in their online community. We have a staff of 5 CM's but want to increase posts from other departments to interact as well. I'm compiling a slide deck portraying the rules of engagement for our staff. Thanks in advance!