Conduct some research. The best way to learn how to identify butterflies is to read up on the different species and become familiar with their unique characteristics. An excellent resource is Robert Michael Pyle's "North Audubon Society Field Guide to North American Butterflies."
Carry a notebook around and write down distinctive colorings and markings when you come across a butterfly you can't identify. Use binoculars to get a close-up view of colors and any distinctive markings on the forewing and hindwing, as well as the shape of the wing and whether the wing's edges are smooth or wavy. Visit the Discover Life website and use the online butterfly identification tool that enables you to find a particular species based on butterflies' physical characteristics.
Identify the various species of butterfly that are common to your area. This narrows down the field, making it easier to identify any butterflies you encounter when out and about. The Agriades cassiope (Heather Blue) butterfly, for example, is commonly found in California, while the Callophrys gryneus (Olive Hairstreak) is found in Kentucky. The Discover Life website has an free research tool to identify butterflies by their geographical location.
Photograph the butterfly you want to identify and submit it to the Butterflies and Moths of North America website. Write down the date when you took the photograph and the butterfly's exact location. The website will add your sighting to its database if a regional coordinator can identity the butterfly's species.