Lately, I've been making it a habit to group everything, from typographic properties, to color, to layout stuff, and I write everything (except the first curly bracket) on a new line, e.g. like so:
background: rgb(35,35,35) url(image.png) no-repeat 0 0;
text-shadow:1px 0 1px rgba(0,0,0,.8);
The order is:
a) Colors and typographic styles
b) Element dimensions
c) Element positioning/floating, etc.
I find I can scan the properties more easily when they're grouped by what they affect.
Furthermore, I group all CSS rules based on what they do, so #header, #nav, #footer, #content, #sidebar, .columns are grouped as layout styles, link styles, headings, paragraphs, lists, etc. are grouped as typographic styles, and page-specific styles are grouped separately.