*Very rough work in progress*
If you think that telling each newbie everything about h2g2 in the first post isn't a good idea (and there are very good reasons why this would be the case) then think about saying first 'what brought you to h2g2' and if you do engage someone in a conversation, then you can tailor your suggestions to that individual. They might say I'm a fan of Douglas Adams, or I'm interested in writing, or I came here via google/the BBC homepage, I heard a trailer and wanted to find out more.
Invite Newbies to Comment in the Writing Workshop
Shepherd newbies to comment in the Writing Workshop, because PR can quite intimidating. Sometimes it is unfriendly because Researchers submit entries to PR well before they're ready. PR is for finished entries. Scouts and other people populating PR spend a lot of time trying to persuade people to move entries out because entries are unsuitable, or they come across entries that have been posted by someone who clears off never to be seen again and it's frustrating. And it, hopefully, would begin a cultural change whereby writing workshop would be populated by enough people to make it an attractive prospect and a usable forum. Treat it as an apprentice forum.
Encouraging Newbies to Write for the Edited Guide
Please encourage new Researchers who's interested in writing to read the writing-guidelines and writing-beginners. That would be great and you are wonderful people.
Suggest that they write something that they know something about. Giving an example helps: their local town, aspect of job or hobby.
(Am happy to include links to Guides to writing about specific topics...)