The positioning of feeders relies on the geographical position of the area, and will vary on the layout, size and fauna of the site. Wide open spaces, or if water is close by, living in a city or country; will all change the variety and types of birds you will attract.
The first primary factor to consider is the safety of the birds. If you or your neighbours have cats or other bird predators, then consider positioning your table or feeder away from close cover. Small birds like to fly into a tree or shrub and then fly to and fro to the feeding station. If the feeder is in the open the birds feel more secure when feeding. The types of plants that are in the area have an influence on the variety of birds and wildlife that will inhabit the area. Remember, the 'birds eye view' doesn't differentiate between your garden and that of your neighbours.
Even in the cities there can be a large diversity of woodland. So a balcony can be an ideal spot to feed Finches, Tits and Sparrows. If you have enough room for a window box, then plants will attract the birds and feeders that stick to windows are designed for such locations. If you have a larger space, then a range of plant and tree species will invite a wider variety of birds.
Plants that produce seeds, berries and fruits are to be considered, all of which are a natural food source. Allocate a sector of your garden to grow wild, even dead trees offer materials and nesting sites for birds as well as providing habitat for small mammals