Most people younger than 65 get health insurance through a job. Employee group plans vary enormously in cost and scope of benefits.

To make the most of your plan, start by finding out who in your company administers it (probably someone in the human resources department, if there is one) and ask for a description, often called a Summary of Benefits. Make sure it answers these questions:

Find out exactly what's covered and any limitations, too. For example, some plans limit the number of rehabilitation visits they'll pay for, or charge a higher co-insurance for certain drugs.

Those include your deductible, co-payments, and co-insurance.

In almost every group health plan nowadays, you have to use doctors, labs, clinics, and hospitals within its network to get the best price. You can probably look up the participating providers nearest you on your plan's website.

You'll pay less for drugs if you stick with your plan's formulary, or list of preferred medications. The plan's website might have the list, but double-check with your provider or pharmacy because networks and pharmacies can change without warning. Ask especially about any drugs you take regularly.

Health-savings accounts (HSAs), health-reimbursement arrangements (HRAs), and flexible-spending accounts (FSAs) provide different ways to defray out-of-pocket health expenses. Each has its own set of rules and restrictions.

Most large companies and some mid-sized ones don't buy insurance for their workers. They self-insure, meaning they pay for their employees' health expenses on their own, contracting with health insurers only to handle claims and supply a network of providers. This matters because your rights and protections vary depending on what kind of insurance you have. You can't tell from your plan documents or membership card whether your plan is self-insured or not; you have to ask your plan administrator.

The Affordable Care Act set up new consumer protections, some of which apply only to "new" plans, aka "nongrandfathered" plans. Your plan is required to tell you whether or not it is grandfathered.

Many larger employers offer a choice of two or more plans. In most cases you can switch to a different plan or sign up for one only during your employer's annual open enrollment period, usually in the fall. But under certain circumstances, known as special enrollment opportunities, you can join your company's plan at any time. An example: If you get coverage through your spouse's group plan instead of your own, and then your spouse loses or quits his or her job, you can sign up for your own employer's plan without waiting for open enrollment.

Your right to appeal primarily depends on what state you live in and whether your plan is self-insured or fully insured. The Affordable Care Act has expanded consumer appeal rights, but changes are being phased in gradually and are complex. If your health plan turns down a benefit, it will usually give you an explanation of benefits or a denial notice stating the reason and telling you how you can appeal.