Every new user gets a welcome PM mentioning the trust system and linking to this blog post, explaining that new users may be temporarily limited for safety reasons. They are also invited to start an optional interactive training conversation with discobot.
Upon transition to trust level 1, users are sent a congratulatory PM which also links to this blog post and invites the user to fill out their user profile, or start a new topic.
Upon transition to trust level 2, users a sent another congratulatory PM which also links to this blog post, as well as the tips and tricks blog post.
Upon transition to trust level 3, users are sent a longer form PM describing their new abilities and inviting them to the lounge category to meet their fellow TL3 community members. This PM also links here to this blog post.
(It’s also worth mentioning that Discourse starts in “bootstrap mode” where the first 50 users who sign up are automatically granted TL1, and daily digests, to promote growth of the community via early adopters.)