For designing a Mock-up for a web site, what from Adobe PS required?

for a web designer for designing a Mock-up for a web site, what from Adobe PS required?

eg. Selections, Layers, Slicing, Guides, … knowledge, well, is it needed anything else?

I am
web developer

Tuts+ have a free online video course on Photoshop CS6 for Web Designers. It is probably a good starting point. Good luck!