You may be new to medicare, or have been on medicare for a while. No matter your situation, it can all be very confusing. What does medicare cover? What's the best plan for my situation? What do supplements cover? My health isn't great, would I even qualify for a supplement? Do I need prescription coverage (Part D)? What's the difference between a supplement and a medicare advantage plan? Would an advantage plan be good for my situation? When can I sign up for supplement or advantage plan or a prescription plan? How will changes in medicare affect me? These are all very good questions.
The best way to get these and other questions answered, is to find a professional who specializes in this field. Your local insurance agent who handles your cars and home, may be a great guy, but may not be the most qualified to answer all of these questions. An agent that is "captive" to one insurance company, will probably not be the most objective in finding you the right policy for your particular situation. You should find an "independent" agent who specializes in senior insurance and medicare products. This "expert" can explain everything to you in detail, answer these and any other questions you may have, and will be able to find the best product for you. With access to multiple companies, he will also be able to find you the best rate. After you have your policy, you will still have access to his wealth of information and expertise in the field, should any questions arise.
To sum it up, find a professional!