I tend to have some which stay put and are 'for the birds' all year round and then have some which are for photography.
The 'photography' ones change and move around depending on the time of year because of the sun creating shade in different parts of the garden. Also different bushes and trees change colour or drop their leaves and obviously different birds visit.
This is just an example of a lazy one I sometimes stick by the kitchen window if i know I'll be at home for a few days without any time for photography. It's normally about 12 feet away and comes in very handy in the winter when it's freezing or raining as that's when many birds feed. It's also nice to have somewhere you can quickly grab a shot if something a bit unusual visits.
In terms of the feeders set up for photography I think about:
Is the background natural and far enough behind the subject so I'll get a nice out of focus backdrop even if I want to stop down the aperture for greater dof on larger birds ?
Will the light be from behind me when I'm going to be shooting ?
Can I avoid sky as a background which makes life difficult ?
Have I chosen the correct style of perch to suit the type of bird that is going to come to the type of food that I've got in place ?
In the one above the branch is just stuck in the ground and then attached to the metal feeder at the other end. This stops the branch wobbling when a bird lands on it which is important as a lot of the time they only land for a second before moving onto the feeders. A thicker branch wouldn't move but some of the tiny garden birds do suit a thin perch. As there's only one branch (all about stacking the odds in your favour) I don't have to worry too much about where the birds are going to land when they form a queue so I can set up the camera settings 'more or less' right before the bird arrives.
Then it's just a case of waiting a few mins. If the light changes I'll just keep adjusting the ISO keeping it as low as possible but making sure the resulting shutter speed is going to remain fast enough. Once a few birds are on the feeders the next birds naturally land on the perch. I just try and focus on the eye using centre point focus. The bird will just be middle of the frame but I know there will be room to crop the composition regardless of whether the bird is facing left or right.
The branches I just pick up from anywhere and just chop and change depending on what birds are visiting.
Here's another random feeder elsewhere in the garden. Again there's a variety of branches stuck in the ground to provide perches based on direction of light and background relative to where I shoot from.
I think it's really just trial and error, getting to know your light directions, what the birds eat, which birds visit and when and generally trying to stack the odds in your favour by perhaps removing some alternative feeders and perches whilst you shoot before putting them back again afterwards.
That's just my approach (for the garden at least) but I'd also be keen to know what others do.
