‘Ps Etiquette‘ is a great guide into ‘Do’s’ in Web Design in Photoshop. I’m pretty sure that there could be add a lot more but I really appreciate an effort and point of websites with similar goal.
Another great one is an article from smashing magazine ‘The Lost Art Of Design Etiquette’.
Or I should not miss this one ‘Photoshop, Illustrator or Indesign?’, my favourite. It is simply explained and if followed and read by young designers these days, we would have less posters designed in Photoshop.