1.) By not passing Glass-Steagall in the 1st place.
2.) By not bailing out banks.
Dodd-Frank claims that with their bill, there will no longer be "Too big to fail".
Instead of bailing out banks, we will now start bailing out derivative clearing houses.
Only a moron would assume Dodd-Frank did anything at all to fix the system.
Glass-Steagall is still there.
"Too big to fail" is still there.
Do those 3 things LegendKiller mentioned earlier and you will fix most of the problems with the financial system. Add stop bailing out banks to those 3 things and you will fix 99% of the problems.
Everyone loves to attribute the repeal of Glass-Steagall on the financial crisis but my thesis is that there was so much demand for mortgages and mortgage securities that the bubble pop would have happened with the same severity anyway even if it had never been repealed. Ultimately, the banks would have figured out a way to lend out the money one way or another while side-stepping Glass-Steagall.