Identification of birds in the field is based upon two important sources of information: topography and behavior. Topography describes the external features of birds. Learning the terms that are used to describe bird topography allows an observer to precisely record the characteristics of each bird they see in the field.
Field observations are often limited to quick glimpses of active birds. Two very important identifying features of a bird are the bill/beak and the face.
Practice identifying birds using pictures in your field guide or on the web as well as the birds that you see daily in your environment.