If you're like many Americans, the introduction of Medicare Part D is nothing short of confusing. By May 15 of this year, if you haven't signed up for the program, you could end up without drug coverage, or have to pay the penalty for applying after the deadline. The penalty is a 1% increase in your premium for each month after May 2006 in which you don't enroll.

The following is a step-by-step guide designed to get down to the basics of Medicare Part D, cut through the jargon, and tells you exactly what you need to know.

Step #1: Eligibility. Are you eligible for Medicare's new prescription drug plan? Simply put, if you are eligible for Medicare Part A or Part B, you are eligible for Part D.

Step #2: Cost. What will Medicare Part D cost you? For drug expenses in the range of $0-$250, you pay 100% of the cost. When and if your costs fall between $250-$2,250, the plan pays for 75%, and you pay for 25%.

At this point, the infamous coverage gap, often referred to as the "donut hole," comes into play. Essentially, if your total drug costs, which include what you and the plan pay for prescriptions, exceed $2,250 per year, you pay 100% of your drug costs after that point until you reach $3,600 in out-of-pocket expenses (total $5,100 in drug costs). But after you escape from the "donut hole," you only have to pay for 5% of your drug costs.

What you pay also includes the usual insurance costs associated with a drug plan. If you do not qualify for extra help, you will pay: monthly premiums, a yearly deductible, and co-pay or co-insurance for each prescription.

If you qualify for extra help due to a limited income, you will pay: low or no monthly premiums, low or no yearly deductible, low or no co-pay or co-insurance for each prescription, and you don't have to worry about the coverage gap.

Through Medicare's prescription drug plan, you must choose drug coverage from one of the many private plans made available for the purpose of Medicare Part D. This is usually the point at which people become the most confused. There is a wide range of plans from which to choose, and in the end, the right one for you depends on your unique circumstances. Search for the plan that offers the lowest total costs for the year, including your premiums, deductibles, co-payments or co-insurance for each prescription, and any drug costs you pay during the coverage gap.

Step #3: Drugs Covered. Choosing an insurance plan also requires that you make a selection based on the specific drugs you need. The list of drugs covered is called a formulary. So when determining which plan is best for you, cost is only one consideration ? you must also make a choice based on the type of drugs covered. Generic and brand name drugs are included in the formularies, but if a drug you take is not on the list, you will either have to pay for it in full, or switch to a similar drug that is covered by the plan.

Step #4: Joining. Signing up for a plan is, luckily, easier than you may think. You can either sign up through the plan's website or through http://Medicare.gov. Another option: call the company offering the plan you desire, or call Medicare directly.