Do you already have ideas when you fire up Photoshop? If not, how about some inspiration?
http://inspirationti.me/
http://minimalexhibit.com/
http://beautifulpixels.com/
If you already have several ideas, I recommend getting something down on the canvas as soon as possible. Just start with one element, like a menu for example.
You might also try prototyping with a simple HTML page with embedded styles. This lets you concentrate on one file in your text editor and then move the styles into a stylesheet later.
I also recommend writing some copy before you start designing; that way the content will help dictate the form of the site (e.g., do you need to present a lot of text or only a little?).