There are several different way to squirrel proof a bird feeder, for example when you place a bird feeder outside and in an open area verses hanging from a tree.
The better idea would be to place it hanging from a smooth metal pole instead of a tree so that the squirrels will have a harder time climbing the pole to get to the birdfeeder. The best way is to make sure it is not anywhere that a squirrel could leap off of something to get to the birdfeeder.
The squirrels can eat and eat and never be full. They will feast upon the bird seed in the feeder until the bird feeders are completely empty with no more seed for the birds. You can even buy or design your own feeders so that the opening to the bird seed closes when a certain amount of weight is applied to the bird feeder. Also the types of bird feeders you buy can also determine whether or not the squirrels can get to it. Some of the worst bird feeders you can buy for bird that a lot of squirrels get into are the plastic or wooden bird feeders because the squirrels can chew and claw their way into the feeder until the seed is pouring out on the ground. Another tip to keep squirrels away is to make sure you clean up the old bird seed on the ground under the bird feeders so that the birds do not eat old and rotten seed. The excess seed also attracts the squirrel as a more “fair game” food because it is on the ground. These are a couple useful tips on how to rid your bird feeders of these tree climbing squirrels. I hope they help you as much as they have helped me.
Source of Information on how to Squirrel Proof your Bird Feeders