I found out from the State of Massachusetts government website that gave some information about becoming a firefighter. To become a firefighter, you have to attend the Department of Fire Services - Massachusetts Firefighting Academy. Before you attend the Academy, you have to pass a State Civil Service Exam. http://www.mass.gov/?pageID=eopsterminal&&L=5&L0=Home&L1=Public+Safety+Agencies&L2=Massachusetts+Department+of+Fire+Services&L3=Department+of+Fire+Services&L4=Training+(MFA)&sid=Eeops&b=terminalcontent&f=dfs_mf a_wannabeaff&csid=Eeops
Here's an example of the process required to become a firefighter in Lynn, MA: http://www.lynnfire.org/FAQS/becoming_a_firefighter.htm
Here are some additional informational websites that provide what is required to become a firefighter: http://www.fire-fighter-exam.com/massachusetts-fire-fighter.php
A MA firefighter has put together an e-book that you can order online that might give you some really good insight as well: http://www.fabjob.com/firefighter.html
Once you have digested some of the information provided, I recommend that you think about what type of firefighter you want to be and also visit local firehouses to talk to the chiefs there to find out what they recommend, based on your desired career path, jobs available in the area where you want to work, and the length of time it will take to get certified as a firefighter.
I hope this helps. Please let me know if you need me to clarify anything I've provided.