This is really a technique best to be described by pictures and not words.
You can try getting the book "Photoshop studio techniques" or "Real World Adobe Photoshop". They have a section on hair selection and masking.
yep, that's a good book. teaches how to select fine details like hair and put them as a selection mask.:thumbsup: but it's rather tedious, as it involves pushing the edges of the hair to near overexposed condition to separate the hair details from the background. but it works nicely.
Go to the library and find this book: Photoshop Masking & Compositing by Katrin Eismann. Excellent book :thumbsup:
There are many ways to make hair selection in photoshop, you can use magic wand, pen tool, even extract tool. But there is a very good method that you can use, by using what we call channel selection. Yap we are going to use channel to make a selection, specially a difficult selection, like hair selection. This video will guide you how to use channel selection to make a selection. You can use this technique to make another difficult selection, such us fur or tree. I hope you enjoy this video.