I open the design up and study it for a while, I prefer to take notes on a peice of paper about font sizes/styles/types and colours. Also take down measurements for table widths and heading heights e.t.c., I like making little diagrams to...just for fun

. Oh and I cut up and save background images and other misc. images
After it is all down on paper I normally go into the Main CSS editor and Plug in all the information I noted down earlier.
Then I go to the Homepage and test the skin out...then I spend ages troubleshooting and bug busting till it looks nice. Finally I go through and do all the Icons and Buttons and anything else.
I prefer writing it down on a piece of paper because I find it is far quicker to read off the paper and type directly into the Editor, also means I can enter everything in one go and Hit Save only a few times.