Most people here want to do everything via the command line, but I have a more practical suggestion.
These two programs described below list a great deal of the known command-line customizable features of Mac OS X applications, sorted by application or function. The advantage is the list of functions is provided for you; you don't have to go searching Google to find out what the functions are and the command-line sequences needed to modify each one.
There are several freeware or commercial applications that provide a graphical user interface listing most all of the customization options that can be modified via the Terminal. To activate any of these features, using these progams I'm describing, you do it within the application's GUI and you have no need to use the command line at all. You don't need to know anything about
defaults write or
Two of these apps are:
which is free, and
which has just been updated with new Lion features, and costs US $20.00.
These are programs that I own and use.
Download the free TinkerTool and the trial version of MacPilot and and click through all the tabs to see all the myriad features you can customize. There are too many to list here.