They’re here. The state health insurance marketplaces, a signature feature of the Affordable Care Act, open for business today. More than three years in the making, the marketplaces, or exchanges, allow consumers to compare a range of health plans online that meet the standards of the law, apply for subsidies and pick the best policy for their needs.

Here are a few things to keep in mind.

1. Don’t wait until the last minute to look for a plan.

Open enrollment lasts through March. If you’re uninsured and want coverage to start on Jan. 1, you must sign up by Dec. 15. But don’t wait until the day before to shop, say experts.

“Start early,” says Cheryl Fish-Parcham, deputy director of health policy at Families USA, a consumer advocacy organization. “If you have questions, that’ll give you time to ask them.”

With an estimated 7 million people expected to buy coverage through the exchanges, building in extra time into the enrollment process will also give you breathing room if, as expected, the marketplace experiences some glitches in processing your application, determining your eligibility for subsidies, and the like.

2. Look beyond the premium when figuring potential costs.

When you evaluate marketplace plans, consider your total potential financial exposure, including the plan’s deductible, copayments or coinsurance, and the maximum out-of-pocket amount you could be responsible for every year.

Exchange plans in every state will cover a similar package of 10 “essential health benefits,” but consumers’ proportion of the costs will vary: they’ll pay 40 percent of costs if they enroll in a bronze plan, 30 percent of costs in a silver plan, 20 percent in gold and 10 percent in platinum.

This year only, some plans may have separate deductibles for medical services and prescription drugs. And a recent analysis by Avalere Health of exchange plans in six states found significant variations in prescription drug cost sharing. Ninety percent of bronze-level plans it examined charged 40 percent coinsurance for drugs in tiers 3 and 4, which typically include pricey specialty drugs. Many silver level plans, in contrast, charged flat copayments averaging $70 for drugs in those tiers.

“Make sure the benefits are covered the way you want them to be … and look for limits on services,” says Kevin Lucia, a senior research fellow at Georgetown University’s Center on Health Insurance Reforms. 

3. Check provider networks.

It’s been widely reported that one of the ways that insurers have been able to keep premiums more affordable on the exchanges is by limiting provider networks. If it’s important to you that certain doctors or hospitals be in your network, check those details before signing up.

Smaller isn’t necessarily less desirable, say experts. “If all your providers participate in a narrow network, it’s not a problem,” says Jennifer Tolbert, director of state health reform at the Kaiser Family Foundation. (KHN is an editorially independent program of the foundation.)

4. Estimate your income carefully.

Roughly 80 percent of people who buy exchange plans will qualify for premium tax credits, according to Avalere Health. The credits, available to people with incomes up to 400 percent of the federal poverty level ($45,960 for an individual or $94,200 for a family of four in 2013) will be based on your projected income for next year. They can be sent directly to the insurer, reducing your monthly premium. If your income estimate is too low, however, you could have to repay at tax time any excess amounts you received.

It will be important to monitor your income during the year. Inform the exchange promptly if it changes and you realize your estimate was too high or too low so your tax credit can be adjusted.

5. Don’t be fooled by lookalike websites.

In a handful of states, experts have already encountered websites that look like official state marketplace sites but aren’t. Now that the marketplaces are open, they expect more of these sites to crop up.

“Some could be deceptive but fairly benign [sites] designed to sell legitimate insurance products,” says James Quiggle, a spokesperson at the Coalition Against Insurance Fraud. “Other sites could be malicious and intended to steal your identity.”

One surefire way to ensure that you’re visiting the official health insurance marketplace for your state is through healthcare.gov.  If you live in one of the 34 states in which the federal government is operating the state exchange, you’ll be directed to information about how to get started picking a plan. If you live in one of the 16 states and the District of Columbia that operate their own state exchange, you can link to your state exchange through the federal website. 

Please send comments or ideas for future topics for the Insuring Your Health column to questions@kffhealthnews.org.