Knowledge of the birds being photographed is invaluable. Numerous sources of information are available in books, magazines and on the internet. A great deal of time can be saved by making the effort to learn about your subjects, their habitat, sources of food, habits and migration patterns.
Identification is arguably the most important issue since no photographer would want to publish wrongly labelled images! Some species change their appearance with the seasons or as they mature from juveniles to adulthood. Females and males typically also have different plumage. In some cases identification is easy but in others expert knowledge is required to distinguish, for example, a juvenile of one species from an adult female of another.
Behaviour also changes with the seasons of the year as the priorities of the birds are focused on feeding, mating, nesting etc. Even typical habitat may change. For example, coastal and sea birds that live and feed mostly over water come ashore to nest. Knowing what changes to expect, and when they are likely to occur, can save a lot of wasted time.
It is also worth taking time to listen to the sounds made by birds. Each species has a characteristic song, alarm call, and even mating calls. Learning to identify these, at least for the species of interest, may help to locate the birds concerned. Birds are often heard before they are seen, particularly in dense undergrowth, reed beds, wooded areas etc. Some people even obtain recordings of male mating calls and use them to attract the birds to their location. With patience, this can work well.