Specifying an ADT
Operations (methods) associated with ADT and the access modifiers.
Data structures (variables/data) needed to specify the ADT and the access control for the data structures.
From the point of view of a problem there are three types of methods you should consider : service methods, utility methods and predicate methods.
From the point of view of how they relate to the underlying data structure you should consider: constructors, accessors, and mutators.