A good tutorial about UV unwrapping

Anyone know a good tutorial about UV unwrapping?

Everytime I make something I just stare at the model with completely no idea which seams to mark.
I looked for tutorials on Youtube but couldn’t find one that explains it well with complex models.

Main thing to worry about is overlapping and stretching. There are some old tutorials from the CGcookie archive that still work pretty well. To download these tutorials you will have to sign up with a free account on Cgcookie or they might have some of these on their youtube account.

Thank you!