I think customizing is something one has to learn over the years. Simply because in the beginning you're full up busy just trying to deal with the basics of anything new.
But when you have those locked down, it's a really good idea to look through the ways to customize the apps and utilities you use, to optimize your effectiveness and pleasure of using them. You can read tips on the web, or a book, or just browse through menus and settings/preferences.
Just for example, I've now gotten Mail.app to work very well for me. Love that. But then today I noticed that I missed one thing yet from Eudora: the very simply little window I could have at a corner of the big screen to show me if there's new mail, while impinging as little as possible on my zen-simplicity of screens. The Mail.app main window is simple more complex and graphic.
But suddenly today I had the insight that I could slide the mailbox sidebar out of the way. Most of the time I only look at the Inbox anyway. So done. Much simpler. And it also solved a small issue of fitting all the info from mail headers into the window without making it so long that it covered for vital parts of wallpaper pictures. (No, I'm not detail-oriented!)
And more, the icons on top could be reduced to just small text links. And more-more, I could customize that toolbar, removing those I don't use, and adding several very useful ones, including one which calls forth the mail boxes when I do want them, etcetera.
I usually hide the Dock, since all the mixed color icons are ugly. So that prohibits Mail.app's fine feature of showing the number of new messages in the Dock icon. I wonder if anybody makes a menu item for that?
Update: Sometimes you just have to get the thought, and look! They do indeed. Yipee. So now I don't even need the app on the screen to keep an eye on new mail.
Ahh. Clarity and simplicity, gotta love it.
Here's a new screenshot (with a different pic from my photo contest last month). Notice a totally clean desktop, no windows or icons. And the little menu bar icon with mail count, which turns from black to red when it goes above zero. Nice touch.