I'm Co-Chair of EA Bath Uni Group, and therefore manage the WhatsApp community for it. A common problem people have in university society group chats is that scammers and bots often join, so to prevent this, every time someone requests to join the group chats, I message them and ask if they are a real student.
If they are a real student, I then ask them how they heard about EA, and usually follow up with something like 

'Oh, that's really cool! Would you be okay to meet so I can explain what EA is about and what EA Bath offers? Or alternatively chat on text / have a call?'

In our 1-1, I summarise my intro talk as a summary of what EA is, and then explain our fellowship that we are running at the university, and finish up by showing some EA resources (e.g. EA Forum, 80K Problem Profiles). This then usually results in them attending at least one session – with a few attending more. 

I think this is really effective for reducing friction when asking for 1-1s, as it makes it seem a lot more casual and gives a purpose to the conversation, and although it would not replace any other methods of community building, I think it is a good addition that may have been overlooked.