The most valuable investment one can make is in a bunch of three-ring binders (they can be used) and a hold puncher. But here's the trick. Every time a bank or credit card statement, utility bill, pay slip, tax notice, or other of the myriad of letters come in the mail, we punch holes in the paper and assign them to an appropriate binder.
This seems really simple, but it is almost mind-boggling how powerful this act is.
First, this means that we can now find any piece of financial information on ourselves quickly and easily, without having to sort through a mountain of papers. Secondly, it means that as we're punching holes in our bills to put them into their respective binders, we're peeking at the details regularly and are more likely to spot any irregularities.
With a picture of our wealth, we can make plans for accruing more of it and protecting it for future generations. Rockefeller probably started off just by doing this...
