well, you need to try to get a bird perched up in a tree.., then try to shoot them when you can see an eye, or both eyes.
It's always good to go in an area, (park) where there are always lots of people, the birds there are much more co-operative. Some like the attention, and pose! Pick a bright day, and if its cloudy, wait for the sun to come through..
Also, a key to shooting birds is to try to get the background as far as possible away from the bird, shoot at full 300 mm, and if you have time, move around, and creare a nice colour for the bg. enough tips from me, Eric and the rest of the guys can please add to this.
The hardest part is trying to get them to look at you and stay still until you get them in focus. Also try to get down to there level when they are this low. Sometimes if you know they are around you have to sit very still and wait for them to come to you and hope they land where there is good light and you can get a clear shot. Patients and be prepared to shoot in an instant, blink and they will be gone. Also you can throw out some bird seed and wait for them to come and get it.
Patience is one thing I use. I will just stand or sit, or even lay on the ground, and just wait and wait. Sometimes to get an critters attention, I will toss something small out of sight, to get the little guy to look. Sometimes they give that startled, curious look, and I snap the pic. Im not as lucky with the birds as the two masters above, but I will wait till they land on a branch, and hope the lighting is good enough.
Just keep practising, and eventually the pics will fall into place.
maybe start by shooting ducks on your local pond where they are use to people hand feeding them with bread. you can get really close and pick your shot.
I know the "WHERE" but am still learning the "HOW"