How do I get started with designing new/existing layouts in Plone?

Taken from various posts on the Plone mailing list ( http://www.nabble.com/Plone-f6741.html ) 
 Stan McFarland wrote: 
 “The short answer is that you can make Plone look any way you want with a combination of template customization and CSS . You just need to learn how to do it. Andy McKay’s “The Definitive Guide to Plone” is a good place to start, as well as plone.org.†
 J Cameron Cooper wrote: 
 “The best way is to start with the Plone pages, which have a fairly standard and general template, and customize them with CSS . 
 If you want to work an existing design into Plone, you will have to do some slightly trickier stuff. (Which, basically, is replacing main_template with your own structure, though preserving the “signature” of main_template.)†
 Peter Fraterdeus wrote: 
 “I highly recommend that you read the docs section in plone.org as a starting place for ‘skins’ customization, and best practices for building a “site product” which will instantiate your customizations. 
 “After that, it’s probably best to have a good look at the way that the “main_template” is constructed and how the various layers of CSS are used to modify the look of the site. (on your *nix box, try “locate CMFPlone/skins/plone_templates/main_template.pt” or find it in the ZMI ).†
 Matt Bowen wrote: 
 “Plone uses Python for logic, Zope Page Templates for layout, and the Zope Object Database. If you don’t know Python, you’ll want to learn it — without it, you will be limited in your customizing. People seem to like Dive Into Python [ http://www.diveintopython.org/ ], but there are lots of good tutorials online, and it’s a very nice language. ZPT you’ll pick up from the book and the tutorials. 
 Finally, definitely check out the many, many good plone videos on Plone.org, at http://plone.org/about/movies and http://plone.org/events/conferences/seattle-2006/presentations/session-videos . There is a lot of good stuff there about all aspects of customization.â€