You will need an entry visa to enter Madagascar, these are available for free for tourists on arrival at the airport for visits of 30 days or less. If you want to stay for over than 30 days you will need to pay for it.
Your passport must be valid for at least six months after the last day you will be in Madagascar and you may need to show a ticket to confirm when you are leaving. You should have at least two blank pages in your passport.
Airport security taxes are usually included in your ticket.
See the FAQ on vaccinations and yellow fever requirements.