First, PSD's that assume text length. For example, if you have three call-out boxes with a title and some text to follow, don't assume that the title will always be one line and the text will always be the same length. Instead, figure out what this will all look like when you do have very uneven amounts of text. Do we center it vertically? Do we abbreviate it?
Second, PSD's that don't assume a responsive design. Sure, working directly in the medium (HTML/CSS) would solve this, but you can still provide some direction here. Tell me how the columns should be laid out. Which parts of the site should expand/collapse with size, which parts can be hidden, etc.
Third, and this goes without saying, but clean up the PSD layer names and groupings. Layer 1, Layer 2, etc. is not a great convention for this.
Fourth, show me the unusual cases. I know the clients always want to focus on the prominent pages, like the home page, the product listing, etc. Those are impo