Hello,
Well first off the bat I would say to use firefox with the firebug plugin installed (if you don't already do this). The firebug plugin will allow you to actually "inspect" a webpage. This means you click the little inspect button and start hovering over items on the website, for example the logo. You hover over it click and then in the firebug window it will show you want HTML makes this up, DIVs, etc and what CSS corresponds to it (including the CSS file it is being pulled from).
With firebug you can also change entities temporarily, you can delete images, change the height on a div, etc. So you can see exactly how or what a change can look like. Pretty much the closest you'll get to visual CSSing.
For some tutorials, etc
http://www.w3schools.com/ is a great place to start.
I hope this helps.
Regards,