I have been on other non-crypto related forums where you were redirected to the rules after registering an account. There was a countdown of 10-20 or more seconds where you had to stay on the page before you could close it and confirm that you read the rules. You cant force anyone to read what is written, but it's still a nice initiative.
I prefer the quiz idea which has been thrown around a few times. If you wanted you could actually get pretty fancy with it, for example during the quiz you could list the rules simialr to the unofficial guidelines that mprep has written up, and then ask them to copy, and paste the rule which talks about plagiarism into a checkbox to advance, upon doing that you could then give them a pop up, and state plagiarism or copy, and pasting for those unfamiliar with the term is disallowed, and will result in a ban. You could probably do this via a pop up on the screen, while it is allowing, and some people will likely block it, this would be a pretty neat interactive quiz which would educate people a little better.