You must understand the requirements for your product, and analyze how these requirements broadly map to the Engine's eligibility/objective/tag concepts before starting implementation.
Typically, the requirements for eligibility/entitlement are enshrined in legislation, and so the task of implementing the requirements is, to a certain extent, a translation exercise (albeit a complex one). We note this here as the tasks described later in this document (for key decision factors and decision details) differ in nature.
The following steps should aid your analysis.