A great practical suggestion comes in the recent book: "The Second Estate" by Ray Madoff. It is an excellent analysis of the changes to tax policy in the US that have gotten us here. (Yes, I know this isn't just a US problem, but the US is the most important part.) One key suggestion is just to make transferring money into any trust (any!) a taxable event so that capital gains must be realized.

It sounds trivial but the effect to various tax evasion strategies is very important. It's also something that really ought to be uncontroversial. Read the book!

Using an asset as debt-collateral triggering gains being realized would be good too. As would unifying the income and capital gains tax.

I disagree with TFA's idea that a wealth tax is the best solution. IMO wealth is easier to hide than income, it's just that nobody bothers right now with there being no wealth tax.