There's a lot of advice about the best ways to prepare for retirement, and it can sometimes be tough to distinguish the good from the bad. Especially considering everyone's situation is different and people need to tailor their financial planning to fit their needs, there are not many hard-and-fast rules for saving for life after work.

There are a few, however, that are not as helpful as you may think. These are sneaky in that they often seem like good ideas, but in reality, they can potentially do more harm to your finances than good. Here are three retirement rules you shouldn't follow:

Older woman looking at a laptop and documents

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1. The 4% rule is the best plan for retirement withdrawals

The 4% rule is one of the most commonly cited tenets for figuring out how much of your retirement fund you can safely withdraw each year. It states that you can withdraw 4% of your total savings during the first year of retirement, then adjust that number each following year to account for inflation. In theory, by following this rule, your savings should last at least 30 years.

But there are a few problems with this. First, it assumes your investment portfolio is made up of 60% stocks and 40% bonds. If your assets are allocated differently, the 4% rule may not work. Also, back when the rule was developed in the 1990s, bond interest rates were higher than they are now -- meaning that even if you follow the 4% rule to a tee, there's still a chance you'll run out of money too soon.

Another potential issue with the 4% rule is that it assumes you'll be spending the same amount of money year after year in retirement. In reality, though, roughly 80% of older adults see their spending change significantly throughout retirement, according to a study from J.P. Morgan.

Retirees will often spend more in their early years of retirement, traveling and fulfilling other wishes on a bucket list. They may then see their spending taper as they settle into their senior years, before it surges again later in life as expensive health issues develop.

Some of these costs will be out of your control, so it may not be realistic to assume you'll be able to withdraw the same amount from your savings every year. It may be wiser to consult a financial adviser to tailor a spending plan for your unique retirement.

2. You must pay off all your debt before retiring

Many experts advise workers to make sure they're debt-free before they retire, but that suggestion can potentially be dangerous for a couple of reasons.

First, it may cause you to delay retiring so long that you don't get to fully enjoy your senior years. If you're drowning in debt and can't afford retirement, that's one thing. But if you can afford to continue making your debt repayments in retirement, you don't necessarily need to wait until you're 100% debt-free to retire.

The second problem with this rule is that it assumes all debt is bad debt. While no debt is necessarily great, not all debt is created equal -- and sometimes, you're better off putting your money toward other financial goals.

For example, say the only debt you have left is a mortgage with a 4% interest rate. You could also be investing your extra cash in your retirement fund, which is earning a 7% annual rate of return. In this case, your money would make a bigger impact in your retirement fund -- while still making the minimum monthly payments on your mortgage, of course. Even though it will take you longer to pay off your mortgage this way, if you were to focus on your debt over saving for retirement, you'd be missing out on precious time to save for the future -- time you'll never get back.

One caveat to this rule is if you're loaded with high-interest debt, like from credit cards, which can carry annual interest rates of 15% to 20% or more. If you don't get it under control quickly, your interest payments can snowball and you'll end up digging yourself deeper into a hole. In this scenario, it's wise to pay off all your high-interest debt before you retire. But with lower-interest debt, you don't necessarily need to delay retirement until it's completely paid off.

3. You should plan to spend less in retirement than you do now

One key factor in retirement planning is how much you expect to spend each year. The oft-cited guideline is to assume you'll spend about 75% to 85% of what you do now. But that can be a risky assumption.

Some people will end up spending less in retirement than they did during their working years, but not everyone. The best way to gauge your future spending is to create a retirement budget.

Try your best to come up with an estimate that's as accurate as possible. Think about the costs that will be reduced or even eliminated (like dry cleaning your business attire or your daily commute), but don't forget about costs that may increase -- like travel or expensive new hobbies.

Your estimate doesn't need to be 100% accurate, but if you blindly assume you'll spend less in retirement, you could be in for a nasty surprise.

There's no one-size-fits-all approach to saving for retirement, so it can be a challenge to know whether you're on the right path. But avoid these common (and potentially dangerous) rules, and you'll have a better chance.