Cats will try to use trees and other obstacles as jump-off points to catch your birds. Squirrels will also use them to try to get to a feeder. It is best to keep the feeder about 4 yards from any tree or obstacle. Expect feathers, seed shells, and droppings and select a location where clean-up will not be an issue. If you have squirrels in your neighborhood, expect unwanted visitors.
Squirrels especially love sunflower seeds and peanuts.
You should invest in a squirrel proof feeder. These will generally come with either a squirrel baffle or a wire mesh around the feeder. Be sure to clean your seed feeders atleast once every two weeks to prevent spoilage and disease. Often seed can become moldy, and diseases such as salmonella can grow in moldy, wet seed. If you have a hummingbird feeder, be sure to clean it atleast once per week.