How do I change the home screen? Add new shortcuts? delete current shortcuts? add weather report? digital clock?
Long press on anything on your homescreen (rather than blank space), and you'll see that the dock bar at the bottom turns into a trash can. Drag whatever you're pressing on over the trash can (it will turn red when you have it right) and it will be removed.
Long press on any blank space on your home screen and select Widgets to add new stuff.
You can also download a lot from the Market. Take a look at the screenshots thread, a lot of Widgets are explained there so you should be able to see what a lot of different stuff is and choose what you like from there.
home++ has a digital flip clock at the top of the main screen and a super cool power strip at the bottom that can alleviate clutter from shortcuts on the home screen. It's also free in the market.