I would personally go with a "Best Practices" page that streamlines the info. I have a very long history of doing volunteer work of various sorts. Some of the early observations are things I am familiar with but I find this paper rather clunky.
I suspect there are no easy answers for some of the barriers they list. (For example, I feel like "lacks the skill to do the job" is probably not something the project manager can or should solve, anymore than a hiring manager should take just anyone who wants the job even though they aren't qualified.) But the social piece is something I can break down for you into basically two key points:
1) Greet people warmly at the door.
People who get that initial "Hi! How are you? We are so happy you dropped by!" kind of response are much, much more likely to keep coming back, even if it takes a bit to figure out where they fit in. Folks who get the cold shoulder often just disappear, never to be heard from again.
2) Never let any question go completely unanswered.
If it does not get a meaningful answer in a timely fashion, then the person in charge should at least drop the person a note to say "I don't know the answer." (When I had a directorship on a voluntary health and welfare organization trying to make the transition to full scale charity, my rule of thumb was that if it had no response after 3 days, I would step in and say something, even if I had no answer.) Depending upon the environment in question, that sometimes bumps the question and allows others to notice who may have missed it due to being away, busy, whatever. So, sometimes just answering nominally will get it answered meaningfully by another but even if it doesn't, the person doesn't wind up feeling like they are out in social Siberia and afraid to speak up again.