A 401(k) is a valuable retirement account that comes with great tax benefits and other perks. It's one of the most popular accounts for saving for retirement because it's also very convenient. But while investing in a 401(k) is easy, that doesn't mean you don't need to make certain you're making smart choices about when and how you use this account. 

To ensure you're doing the right things with your workplace 401(k), you'll need to know the answers to these three big questions. 

Colorful letters spelling out 401(k) sitting next to piggy bank.

Image source: Getty Images.

1. How much are you contributing?

First and foremost, you need to know how much you're investing in your 401(k) and make sure it's the right amount. Chances are you signed up to contribute when you first started your job and may not have reconsidered your contributions since then. That could be a big mistake if you're investing too little. 

You can find out your contribution amount by looking at your online account or asking your 401(k) administrator if you aren't sure. Make certain you're investing at least enough to max out any matching funds your employer provides. Beyond that, you'll have to decide how much of your retirement contributions you want to put into your 401(k) versus other types of tax-advantaged accounts, such as an IRA.

You should ideally make contributions to retirement accounts that add up to around 15% of your income. If you don't have any other tax-advantaged account, be sure you're putting that much into your 401(k). If you aren't already hitting that target, aim to work up to it by increasing your contribution amount when you get raises and as you reduce spending by looking carefully at your budget. 

2. What are you invested in?

Contributing money to your 401(k) is just the first step -- you also need to invest the contributions you make. And you'll want to make certain you're putting an appropriate percentage of the money into the stock market.

Many 401(k)s allow you to invest in target-date funds, which automatically invest your money in the right mix of assets based on your age. If you don't want to use a target date fund (which sometimes comes with higher fees) or your account doesn't offer one, review the investments available and see what makes sense given your age and risk tolerance.

In many cases, it makes sense to subtract your age from 110 to determine the percentage of your portfolio to invest in stocks. But you can also use other methods of determining your risk tolerance and deciding on an appropriate asset allocation. Your 401(k) should have a list of funds you can choose to invest in that allow you to get exposure to both equities and more conservative investments such as bonds. Look for funds with low fees and adjust your asset allocation as you age. 

3. How much are your investment fees? 

Speaking of "low fees," some funds in your 401(k) may charge a higher management fee than others. And your 401(k) itself may also impose an administrative fee. Fees can eat into your effective rate of return and make it harder to save enough for a secure retirement, so you'll want to do what you can to minimize them whenever possible. If your 401(k) only allows you to invest in high-fee investments or you pay a lot just to have the account open, consider investing only enough in it to max out your employer match and then putting the rest of your retirement contributions into an IRA. 

By paying attention to what your fees are, choosing the right mix of investments, and contributing enough of your income, you can use your 401(k) to set you up for the financial security you deserve as a retiree.