Given what you have said, where should a US-based person put their savings in order to (1) keep up with inflation, and (2) make a reasonable return (somewhere in the 6-10% range)?
Retail investors are unlikely to beat the market as a whole, so just buy the entire market, hold it forever and keep costs low. For instance, Vanguard's Total Stock Market fund holds almost every publicly traded stock in America (~3700) and is dirt cheap.
John Bogle, founder of Vanguard, recommends "your age in bonds". So if you're 20, make bonds 20% of your portfolio. Some adjust this up or down depending on their appetite for risk (I think age minus 10 is the common advice from Vanguard now).
A straightforward bond/stock split has been recommended, and it's probably the simplest but even then there are questions of which bond fund/ETF and which index/equity fund/ETF to choose.
Creating a plan requires understanding what your tolerance for risk is. It doesn't have to take a lot of time [1] and some basic reading and math will enable you to pick what's right for you. Basically, are you willing to tolerate more volatility (i.e. variability in year-to-year returns) in exchange for higher returns in the long-term?
1. http://www.finiki.org/wiki/Portfolio_design_and_construction
>There's the Shift Index by Deloitte's Center for the Edge, which shows a long-term secular decline in return on invested capital (ROIC) from 1965 to 2009 by 75%. It's fallen from 6.2% to 1.3%, and is on track to negative returns in a little over a decade. http://redd.it/1y3z3n
The comment you are responding too is asking what to do assuming the top-level comment is correct, and the total return on invested capital is, in fact, declining.
Buying a low load index fund is advice that few people are going to argue with, but it doesn't answer the question.
Both financial vehicles and cash presume that the economic system will sustain itself. There's always the possibility it won't.
You would want to tailor your asset allocation to match your risk profile. Furthermore, your timeline (i.e. when you will need access to the funds) will affect your asset choices. If you have a short amount of time (less than five years) it's usually too risky to have a high or even moderate exposure to equities. In fact, if I knew that I would need to spend the money within five years, I would keep a large percentage in safe (i.e. guaranteed) investments.
That will give you protection from volatility in any one security. You won't be protected against general market (or financial system) risk.
There are several bond issues which are specifically inflation-indexed, e.g., TIPS for the US:
https://en.wikipedia.org/wiki/Treasury_security#TIPS
https://en.wikipedia.org/wiki/Inflation-indexed_bond
You're not going to find a 6-10% return on these though, generally.