Attached Link: Tutorial

You could take a look at this video tutorial for one way that it can be done.  This way works for quite complicated selections: eg  hair, etc.

As said above the best method depends upon the photograph and time you have to do it.

Note: The link is to a 30Mb file - it is a 23 min. tutorial.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html