You're looking to learn how to invest for retirement, and I'm guessing that's because you're already saving money and are now trying to figure out how best to make it work for you. If so, congratulations -- you're in a better place than most Americans, who have essentially no savings.

I'm going to be blunt: There is no one-size-fits-all "best" way to invest for retirement. It's mostly contextual based on how long you have until you actually retire, how much you can save, and how much money you need. And while there are plenty of rules of thumb out there for how to spend down your retirement savings, all of them have flaws, so you'll need to stay aware and think through what makes the most sense to you. Finally, and crucially, learn and understand your own risk tolerance. While some investments might yield better returns, that's often at the cost of more risk. You have to be able to sleep at night, confident in the security of your portfolio.

Highway sign in front of a partially blue sky reading: "The better way just ahead"

Image source: Getty Images.

With those caveats in mind, here's how I think about investing for retirement, based on how many decades are left between when you start and when you retire.

More than 25 years from retirement: Swing for the fences

If you're thinking about retirement more than 25 years out, you're already ahead of the game. But you've probably read all kinds of stuff out there about asset allocation and subtracting your age from some number (usually 100 or 110) to figure out how much of your portfolio should be in bonds.

My two cents? Ignore all of that. You've got plenty of time to invest, and I think you should take full advantage of stocks' higher return potential. Forget bonds: You don't need safety (assuming you already have cash set aside in an emergency fund) nearly as much as you need growth, so every dollar you invest today will be worth multiple dollars at retirement.

And no, I'm not suggesting you go put a bunch of money into bitcoin, or penny stocks, or trading soybean futures. But small-cap growth stocks might be just the ticket; they're earlier-stage businesses with plenty of upside as they grow into and dominate their niches. Now, to be clear, they're volatile -- and some will go out of business as their businesses crater. But holding a diversified portfolio of small-cap funds should help control for those issues.

If you have the stomach for small-cap investing, the Schwab U.S. Small-Cap ETF (SCHA 0.96%) is a great place to start. Consider mixing a couple of small-cap growth funds with a large-cap growth fund or two, as well as some international exposure for more diversification.

Between 10 and 25 years from retirement: Gradually reduce your risk

As you move closer to retirement, you'll hopefully have a bigger nest egg to protect. As you get closer and closer to that "one decade to go" mark, it'll be increasingly important to think about controlling for risk as you shift toward asset protection. That doesn't mean you should stop investing in stocks -- but rather that you might consider shifting the types of stocks you invest in.

Over time, it may make sense to start layering in blue-chip stocks to provide your portfolio with stability in volatile market times. Dividend Aristocrats, which have raised their dividends annually for at least 25 years running, are another way to reduce volatility and gradually start building portfolio income.

Corporate bond funds also start to make sense as you get closer to retirement. As interest rates increase, bond yields will too -- which can provide some nice, consistent yearly income, and further diversification from the more volatile stocks still occupying a significant portion of your portfolio.

Less than 10 years from retirement: Reallocate assets

As you get closer to retirement (less than a decade away), you'll want to start thinking pretty hard about asset allocation. It's at this point that I start recommending a common rule among financial planners: Take 110 and subtract your age from it; the remaining number represents the percentage of your portfolio that should be held in stocks. (So, if you're 60, then 110-60 = 50 -- meaning 50% of your portfolio should be held in stocks.)

If you're more risk-averse, you might lower 110 to 100. So much, as noted above, depends on context. And you'll likely want to shift your stock-based holdings increasingly away from growth funds and toward the more stable blue-chip stocks and Dividend Aristocrats.

This is a great time to check and make sure that you're on track with your savings -- in part because, once you turn 55, you can save more in tax-advantaged retirement accounts. In 2018, savers aged 55 and up can put an extra $6,000 per year into their 401(k)s, up to a total of $24,500. And they can put an extra $1,000 into their IRAs, up to $6,500. So if your returns haven't been quite what you needed, you can make up some of the difference with some extra savings as you sprint toward the finish line.

Investing after retirement

Once you've retired, things change. You'll shift from adding to your portfolio and gradually begin to withdraw money from it. Your investments should change to reflect that reality.

Most retirees should think about having a couple of years' worth of spending cash in a savings account. That way it's immediately accessible if something happens (like a medical emergency), and it isn't subject to any of the ups and downs of the stock and bond markets. (And hey, a savings account may not pay much, but it still beats $0 in interest from a checking account.)

If you're following the 110 rule (or the 100 rule, or a similar rule), you'll gradually shift your investments away from stocks, and toward bonds or even potentially lower-yield options like CDs.

The most important part of retirement investing

Everything that I've laid out above is one plan you can follow to invest for retirement. It may not work for you, because everyone's different. Treat it as a rough draft that you can bump against your personal circumstances and adjust to fit.

But the key thing that everyone should take away from this is that effective investing for retirement requires making a plan and having time to execute it. So make that plan today -- you'll be glad you did. And here are a few extra retirement investing best practices to help you on your way.