Hi Susan,
To achieve this, you must create a relationship class between your features and the related table. Then, both the feature class and the related table MUST be present in the MXD when publishing your feature service. Everything should be good from that point.
From online help:
Feature services also allow queries on related data. For example, a published map document can have layers and tables that are related through geodatabase relationship classes. In this case, the feature service allows queries on a layer to return objects from the related layer or table. Note that to support queries that return related objects, both the table and the layer involved in the relationship class must be in the published map document. If either the origin and/or destination layer or table is not included in the map document, the relationship is ignored by the feature service.
ArcGIS Help 10.1
Cheers,
Todd