DEAR SAVVY SENIOR: At age 62, I will be retiring at the end of the year and plan to enroll in Obamacare until my Medicare kicks in. Can you offer me any advice on choosing a plan? — Almost Retired

DEAR ALMOST: The new health insurance exchanges — also known as Obamacare — that begin in 2014 will have a significant impact on millions of Americans who need health insurance, especially pre-Medicare retirees and uninsured baby boomers who often have a difficult time finding affordable coverage.

To help ensure you get the best health insurance coverage that fits your needs, here are some things you should know:

Starting Oct. 1, you will be able to shop for health insurance policies, and enroll in one directly through your state’s Health Insurance Marketplace website, over the phone, via mail or in person at a designated center. The coverage will go into effect Jan. 1, 2014.

You can also be reassured to know that federal law prohibits marketplace insurers from denying you coverage or charging you higher rates if you have a pre-existing health condition. But they are permitted to set premiums up to three times higher for applicants over the age of 50, and smokers may be charged up to 50 percent more than nonsmokers.

To help make coverage affordable, sliding scale tax-credits will be available if you earn less than 400 percent of the poverty level — that’s $45,960 for a single person and $62,040 for couples. These tax-credit subsidies will provide immediate savings off your monthly premiums. See the Kaiser Family Foundation online calculator (kff.org/interactive/subsidy-calculator) for a premium estimate.

Every state will have a marketplace, but each state can choose how it will operate. Seventeen states and the District of Columbia will run their own state-based marketplace, seven states will partner with the federal government, and 26 states will offer federal marketplaces. The differences between federal and state programs will be subtle. You will be able to access your state’s marketplace at Healthcare.gov.

To make shopping and comparing a little easier, the health plans will be divided into four different levels — bronze, silver, gold and platinum. The bronze plan will have the lowest monthly premiums but the highest out-of-pocket costs when you need care, while the platinum plans will have the highest premiums with the lowest out-of-pocket costs.

You will also have a variety of health insurance companies to select from. To help you evaluate insurers, the nonprofit National Committee for Quality Assurance offers online “report cards” at ncqa.org that can help you narrow your choices.

Because most plans will be managed-care policies such as HMOs or PPOs that require you to get your care within a network of providers, you’ll want to make sure that the doctors and hospitals you typically use are covered in the plans you’re considering. The new marketplace plans are expected to offer fewer choices of health-care providers, and who’s included may vary quite a bit.

You also need to find out what happens if you want to use a doctor or hospital outside a plan’s network. Will you have to get a referral or pay more to get these services, or will it even be covered at all?

Also check the plan’s formulary, which is the list of prescription drugs they cover, to be sure all the medications you take are covered without excessive co-pays or requirements that you try less expensive drugs first.

If you need some help with all this, the Marketplace Help Center offers a toll-free helpline at (800) 318-2596. Or, if you’d rather get face-to-face assistance, there will be designated centers set up with trained and certified navigators, counselors and application aides to help you, along with insurance agents and brokers. To find help in your area, call the Marketplace Help Center after Oct. 1 for a referral.

Send your senior questions to: Savvy Senior, P.O. Box 5443, Norman, OK 73070, or visit SavvySenior.org. Jim Miller is a contributor to the NBC “Today” show and author of “The Savvy Senior” book.