Investing is one of the simplest, most time-tested ways to build wealth. In these days of low-cost index ETFs, fractional share investing, and $0 commission trades, anyone with just a few extra dollars a day on his or her hands can start down the path to potentially becoming a millionaire.

This raises a key question: If investing to build wealth is so simple, why isn't everyone on his or her way to getting rich? One key reason is that money tends to burn a hole in people's pockets. If they have it, they spend it, and then it stops being available to invest. 

And that brings me to my No. 1 secret to getting rich: Make investing automatic.

Standing behind a series of stock charts, a robot touches a finger to its head.

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The biggest benefits of automated investing

When you make investing automatic, your money gets put to work for you every payday without your having to do anything more than the initial transaction you set up. In effect, investing becomes like another bill you're paying, only this is one with the potential to help you get rich. The money leaves your pocket, so it's not burning a hole in it, but instead of being spent, it's being invested in the quest to build wealth on your behalf.

In addition, by making your investing automatic, you're taking advantage of dollar-cost averaging to help you get closer to your investment's long-run average returns over time. If you're worried about buying stocks because the market is near all-time highs and afraid it might drop, this can help you get past that fear. After all, if you buy and the market does later drop, it means your next investment buys more shares. And if the market doesn't later drop, you'll be glad you started investing as early as you did.

Take it straight from your paycheck

Surrounded by golden coins at its base, a trophy holds an egg labeled 401k.

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If you have one available to you, investing in your 401(k), 403(b), TSP, or other employer-sponsored retirement account can be one of your best ways to start your automatic investing. For one thing, the paperwork to get started is usually quite simple -- often just a quick Web form or call to your HR manager. For another, the money to invest in your plan can come directly from your paycheck, with no temporary temptation to spend from the cash in your hand or in your bank account along the way.

In addition, your employer might kick in a match for investments you make in your plan, and money invested in qualified employer sponsored plans have tax advantages as well. In all such plans, money in the account grows tax-deferred. In traditional-style plans, you get a tax deduction for contributing, while for Roth style plans, money you contribute can come out completely tax free once you reach retirement age. 

That combination means that not only can you very easily make your investing automatic, but you might also just find that you're instantly doubling your money simply by investing it in that plan. That's an incredible way to kickstart your journey to investing wealth, and all it takes is a few minutes of your time to set up your contribution. Once it's set up and flowing and a regular part of your pay cycle, there's a good chance you won't even miss the cash that's being put to work for you.

Investing that money if you're not a market pro

blocks with ETFS, Stocks, and Bonds written on them

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Of course, the act of socking money away is important, but to truly get yourself over the line, you need to earn a decent return on your money. While there are no guarantees in investing, over the long haul, the stock market has delivered returns near a 10% annualized rate.  That's enough to turn a little bit every payday into a pretty sizable nest egg over the course of your career, but it comes with risks attached.

One of the key risks is that over the short term, the market can go down as well as up. To address that key risk, it's important to only invest money in stock-type investments that you don't think you'll need to spend for at least the next five years. Another key risk is that while stocks overall have provided those great long-term returns, not every stock in the market has done as well. As a result, you'll need a way to spread your investments out across multiple stocks to protect you from the failure of any one business.

The easiest way to do that is to invest your long-term money in a low-cost, broad-based index-type fund. That way, you'll get whatever the market returns over time, aside from an almost imperceptibly small fee. Not only is that a very easy way to get stock market-type returns, but index funds also tend to provide higher returns than funds managed by professional investing managers . As a result, they're an awesome way to invest for long-term returns.

Get started now

Because of the way compounding works, the longer you give your automatic investing strategy to work, the stronger your chances it will work out in your favor. As a result, there's no better time than right now to get yourself ready and then start investing. The sooner you get started, the more time you have on your side and the farther this straightforward strategy can take you.