In Tiger, Expose is very essential feature that most of Mac user need. Upgrading to Leopard, you also get the access to more Spaces. To use these great features easily, you could use Hot Corners.
Hot corners help you activate one of those features whenever you move your mouse to the corner of the screen. And you can easily set up your hot corners. How to set up hot corners?
First of all, go inside Apple ▸ System Preferences… Go to your search box, the one with magnifier at the left, and type in "hot corner" to look for this feature. You will see 2 items highlighted. Choosing either one has the same result.