The Massachusetts state government web sitehas posted some suggestions to keep in mind if you are pursuing a Property Tax Abatement. (You must request an abatement if to lower the tax if you believe the tax assessment on your property is too high.) First, check for the forms you need in your local tax assessor's office. If you'd like to see a printable form on-line, you can click here. You cannot get started without the correct form.
Next, the form needs to be filed at the town hall governing the property before the bill is due. The signature(s) of the owner(s) must be on the form, or the signature of their representative. (If the signature is not the owners', you should provide some proof that the person signing the form has authority to do so. Otherwise it can be rejected easily as an improperly filled out form.)
If mailed, the postmark must be no later than the due date of the assessment bill. If hand delivered, applications must be in the assessors possession by the close of business on the due date.
Some towns have a very complete web site and others are still developing one. Don't rely on the on-line information for your town though,because sometimes it is out of date. A personal call or a visit to your town hall will insure you have current assessment information, and you can also clarify any "special circumstances" that your town may acknowledge or disallow.
You will also need a good estimate of the current value of your property. That can be easily handled by a good local real estate professional that both lists and sells property.