Have you received that hefty packet detailing your health benefits from the human-resources department yet? If not, you’ll likely get one soon, as fall is the time many companies ask their employees to rethink their insurance coverage. And while 80 percent of us will simply check off what we had last year, benefits experts say that can be an expensive mistake. As insurance costs for companies rise, you can bet some of that burden will shift to employees. But by choosing the smartest insurance plan and taking advantage of other ways your employer or insurer can pick up more of the tab, you can still save hundreds of dollars next year.

The catch? You need to invest some time and effort: Read that benefits packet carefully, and visit your insurance company’s Web site or call their customer-service representative. Here, four of the best ways to shave costs.

Choosing the health-insurance plan that will ultimately cost you the least while providing the care you want is no simple task. Most people look at just one number when deciding between insurance options: the monthly contribution their employer charges for coverage, says Richard Ostuw, a consultant with benefits firm Towers Perrin in New York City. But also knowing what you’re likely to spend out-of-pocket in the coming year is crucial.

First off, ask your insurance company’s customer-service department for a tally of fees you paid yourself in 2004, then break them down into co-payments for doctor’s visits, co-pays for prescription drugs, and the like. Remember to factor in what the co-pay would be for an emergency-room visit or hospital stay in case of injury, especially if you participate in active sports.

Two more numbers to pay attention to are your deductible, or the amount you have to pay before your benefits kick in, and your co-insurance, or the percentage of physician’s fees you’re responsible for. Many managed-care plans don’t have a deductible and pay 100 percent of physician’s fees, but you’re restricted on which doctors you can see, so you need to consider how much you’re willing to compromise in your choice of physicians.