Repeal the following legislation in their entirety:
The Financial Services Modernization Act of 1999 (Gramm-Leach-Bliley),
The Commodity Futures Modernization Act of 2000, and
The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010.
If there is a single thing that would prevent another economic collapse in the future, it is the immediate repeal of those three acts.
Of course, nothing is simple, especially with regard to these laws. While it may seem simplistic to throw the laws out in their entirety, it is a fact demonstrated by the negotiation and passage of the third act in the list that any attempt at hashing out the details will be immediately corrupted by those who stand to lose from reinstating the controls set forth in Glass-Steagall.