How Exactly Do You Cut Stocks?

I NEVER learned how to cut stocks. I have been using Photoshop since 2006 and this important thing is one of the few things I NEVER learned. I used to do everything, including deleting pixel by pixel but it took a pretty long time. I have googled many times and I never got any help from it.

I don't know if the "technique" varies from picture to picture, but I just tried to cut this one out and it was awfully hard.

http://stephenkui.com/how-to-cut-out-hair-in-photoshop/

here's a good tutorial, but i guess this case is already solved.
Sooooo... greetings :>