Put 30% in VTI - the Vanguard Total Market Index (basically all US stocks).
Put 30% in EFA - the Europe, Australasia, Far East first world country index.
Put 10% in RWR - an index of U.S. real estate.
Put 10% in RWX - an index of international real estate.
Put 15% in Treasury Inflation Protected Securities.
Leave 5% highly liquid.
Minor variations on this are fine. The key is invest in broad market indices, diversified among stocks and real estate, domestic and internationally, with a bit of cash set aside for rainy days. Any other strategy involves speculation (trying to be smarter than the market), and unless you think you really know what you're doing, you shouldn't speculate.