If you’re on Medicare Part D, this month marks the beginning of the annual enrollment time when beneficiaries can try to pick the plan that provides the best coverage for their prescription drugs. But even though switching plans may sometimes be a smart move, says Dan Mendelson, chief executive of Avalere Health, a consulting firm based in Washington, “seniors are remarkably passive when it comes to changing plans.”

Don’t be. In part because of the health-care overhaul law, there are some changes in the Part D program that may affect your out-of-pocket costs and coverage for 2011. By investing time during the enrollment period — Nov. 15 to Dec. 31 — to evaluate your options on the Medicare website, you can make sure you’re signed up for the plan that’s best for you.