Heres a quick simple way to center a layer perfectly in the middle of another desired layer. I can't stress how useful this is when designing and is super handy. Great shortcut to know.

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For this tutorial I will be centering text in the middle of an image, this works for anything, you do not need to use this affect like I do.

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1) Have what you want to center selected in your layer panel like so.
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1a) With your layer selected, hold Ctrl or Command on Mac and left click the thumbnail of the layer you want to center it too. So for me I want to center my text layer to my background layer. An icon will appear next to your cursor when done correctly. This will select the entire area of your layer.
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2) Make sure you have your move tool selected, it should be your first tool. In Cs6 or below it should look like a cursor and in CC it looks like this.
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2a) Now click the same buttons as I do to center the layer on the image. You can mess around with the other buttons as they just move the layer to the left, right, upper corner and lower corners of the image. Feel free to explore.
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3) Press Ctrl + D to deselect to get rid of the selection around your image. Your layer is now perfectly in the middle of your image!
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I hope this helped and remember this works for centering anything to anything you want. Any questions or need some help, feel free to PM me. @Skates