I'm using StackOverflow and other StackExchange sites for 4 years, I'm a casual user: if all my googling fails, and inescapably got stuck with something, I'll ask, accept and go away when done. I answer questions to share my research only if I think it has better place on the internet than in my notes.txt by finding the appropriate question or by writing a self-answered one.
But until now didn't notice that every site has a nice description what's on-topic, what's not and where to go if your question would better fit elsewhere - in the first position in the help center.
First, naturally for me I only click on the "Help" menu on a program or website, when I got stuck or don't know how to do something on the site: eg. How to format? How to tag? etc. But the site already provides nice hot links to these information on the right side, so I don't need to visit the help center.
Also in the first years I didn't really care. I thought the "Is your questions is about Programming/physics/mathematics/whatever" that appears in the box right side when asking is enough. Then I learned the hard way it isn't. Some new users might not even notice that box because it looks like a banner.
Second, The Tour/About page already contains a vague list what's allowed what not, I usually looked at that and not the detailed one in the help center, because the "Take the Tour" has a large orange wants-me-to-press button on the site when I visit it on the first time (or simply not logged in).
To sum up, I think the current Ask Question page does not provide enough information for new or casual users to post a good on-topic question. So could we put a more attention grabbing link to help/on-topic into the Ask Question page?