Investing in your retirement is crucial, whether you’re in your 30s or your 60s. With most retirements now lasting 25 years or more, a long-term plan is crucial.

A variety of strategies are available; some are worthwhile at any age, and others are more age-specific. How do you determine which is best for you?

Start by understanding your investment options. Retirement investments typically include IRAs, mutual funds, stocks, bonds and money market accounts. Your present age and your expected needs in retirement will determine the amount you invest and how you’ll invest it. Additional sources of retirement income are social security payments and employee pension plans, but the amount of income either of these will generate varies widely.

In order to determine how much annual retirement income you’ll need, review your current budget and expenses. The AARP offers a number of helpful financial worksheets on their website, www.aarp.org. Make a list of all your assets as well as your debts, and draw up a monthly budget sheet. If you’re not sure what you spend each month, keep a record of every penny you spend for the next three months. Then review your spending and decide how much you can afford to put toward retirement. Make it a habit now to live within your means; this skill will only become more valuable once you retire.

Some people assume that their monthly expenses will decrease once they retire. While this may be true of certain expenses, these savings are offset by insurance and health care costs. Also, you may have new expenses associated with a change in lifestyle, such as increased travel or the pursuit of new activities.

Some workers, especially those under 40, assume they can save less for retirement now if they plan to work past age 65. It’s true that an extra few years can give you more time to save and build your assets, but what if you or your spouse develops a chronic disability? Or suppose you simply decide you’re tired of working at 65? To be safe, plan to retire when you’re 65. If you decide to work longer, the extra income will be a bonus to your savings.

It’s common for people in their 30s and early 40s to feel that they simply can’t afford to save for retirement, what with house and car payments, credit card debt and saving for their children’s college funds. But the earlier you begin to save, the more time your money has to grow and the less likely you’ll be scrambling to catch up as you approach retirement. A good rule of thumb is to save 10-15 percent of your pretax income in a tax-deferred retirement plan with a blend of stocks, bonds and mutual funds. Because you can afford to take some risks now, this is also a great time to try out different investment strategies to see which yield the highest return for you. Continue to manage and reduce your debt, stick to your budget, and make saving a habit.

The closer you are to retirement age, the more careful you must be with your investing. If you’re in your late 40s or early 50s and are not on track to reach your retirement goals, you may need to invest 20 percent or more of your income in order to make up for the shortfall. It may even be necessary in this case to consider a more aggressive investment plan, but you should carefully weigh this option against the potential risk of loss.

No matter what your age, you should review your retirement plan every year, and make adjustments as needed. Arrange for automatic deposits into your retirement account so you aren’t tempted to spend what you’ve planned to save, and don’t borrow against your retirement savings. You’ll find it valuable to research your investment options periodically, and you may find that a trusted financial advisor can help you navigate the many choices for retirement planning.