TeX.SX has this welcome post which nicely summarizes the guidelines for writing questions and answers on a Stack Exchange site. They usually link to it when greeting new members. Should we copy it over (with the required adjustments) and do the same? It might be a nice nudge for new members who haven't read the help pages before posting.
I think that linking to the new help pages (by using the shorthand
[help] in the comments) and their various subtopics is probably sufficient.
As long as the people on TeX don't consider it a problem, I would not be opposed to you making a new meta post with specific details that may not be covered in their post, but we already have some "faq" questions on here pertaining to homework, etc.
I think that this is a good idea.
Unlike what the others have said, I think the tour and help centers aren't quite enough to guide the new users. There's a lot of things going in the minds of the newbies. They need to informed about how voting works, how to not get disappointed at downvotes. They should also get to know how to react to posts put on hold. It's a common misconception among newbies that we close their questions because we cannot solve them. This is not the case and it should be notified to the OP.
I'm all in it for writing a welcoming page, let's see what the others think.