Photoshop professionals agree: Selecting people can be tricky, complicated by lighting, hair, focus and environmental issues. In this series, learn the tools and techniques the pros use when making "people selections"in Adobe Photoshop.
Me of what you will learn from this course:
1) It is possible to use gradients in Pixel Masks f fading images out similarly to Feather effects in InDesign.
2) The best combination f selecting hair in Photoshop is Col Range with Refine Edge with the Smart Radius option enabled.
3) Masking can be used f creative compositional effects too. Try using a pixel mask on a Black and White adjustment layer and assign a stroke and drop shadow on it to create an interesting image in an image effect.
4) A good example of using clipping masks in Photoshop is when you clip an image layer onto a text layer. This way the image will be only visible inside the text.
5) There are two types of masks in Illustrat: Clipping mask and Opacity Mask. The main difference between them is that you can only create transitional feathering effects with Opacity Masks.

http://totaltraining.com/ste/essential-skills-f-designers-%C2%AD-making-selections-of-people-in-photoshop/