I've been a supporter of the super-majority requirement for a while (or better yet, the super-duper-majority: 80% or more). It's easy to get 80% of people (hopefully more like 99.999%) to agree murder, rape, kidnapping, arson, etc. are bad. It would be impossible to get 80% to agree to slavery, unjust wars, NSA spying, the Patriot [sic] Act, taxes for wealth redistribution (most of which in the US goes to the über rich banking and corporate crony crowd, not the poor), and other statist dreams.
Another useful trick would be automatic sunset clauses, e.g. every law expires after five years. And the sunset period could be limited by the support gained. E.g. if 60% approve, it lasts a year, if 70%, 2 years, etc.
I also propose the ability to remove bad laws easily (one of the problems we have in the US, e.g. repealing the 1934 National Firearms Act): Repealing a law should consist of proposing the exact law again, but if it fails to pass at any stage, it should not only fail to extend the law, but it should immediately repeal the existing instance of that law.