We've mentioned this before, but it keeps being ignored.
When someone joins a community, you need to get them to participate in an interaction immediately.
Don't waste this first visit by sending a newcomer to their profile page. Too many communities are still doing this. Members will complete their profiles when they want to impress others in the community. They will only want to impress the people they've interacted with.
The next page immediately after registration should be a discussion or activity members can participate in with other members. They do this and enter the notification cycle.
If you get this right, your ratio of newcomers to regulars will skyrocket.