Patience, perseverance, & practice is what it takes to become a good photographer. Be prepared to spend some time in the field and take plenty of photographs and experiment! It is important to know your birds, know where you are likely to find them and what time of year you might expect to see them.
For example, Kingfishers although they are brightly coloured birds they are very hard to see. This is because they are very patient and secretive birds that lurk in the shadows along riverbanks waiting and watching for small fish. When they take flight, they do so at great speed and hence you only get a glimpse of their metallic colour. So you have to have that camera ready!
The Robin on the other hand is almost tame and inquisitive and can be seen in almost all gardens and is easy to locate and photograph.
Avoid placing any subject in the exact centre of a photograph. It is much more visually stimulating to see the bird/object off to one side and facing inward.
In the case of a flying bird, leave space in front of it, so it appears that the bird has somewhere to go.
Incorporating some part of the bird's habitat into the shot usually makes it more interesting and is a simple way to help others understand its natural habitat. If the background is too busy, try to blur the background and make your subject stand out.
Where possible, try to shoot from bird's-eye level rather than taking the picture from above. Many birds are secretive and sensitive to noise and movement so to get closer to birds, it is a good idea to wear dull clothing and to even hide behind vegetation when taking photographs.
Try to have the source of light behind you and to one side.