Check if your video card is compatible with XGL on Video Card support page.

Install nVidia/ATI drivers. (howto)

Open up terminal, and do the following (Applications->Accessories->Terminal)

su

rpm -Uvh http://fedoraxgl.tuxfamily.org/repository/fedora-xgl-repository-1.0-3.noarch.rpm

rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-AL-CAPCOM

yum --enablerepo=fedora-xgl install compiz xorg-x11-server-Xgl

gnome-xgl-switch --enable-xgl --auto

When script asks you, you should answer as "y"

Restart your X server or your computer for the changes to take effect.

Use gset-compiz command to configure your XGL/compiz options, or use GNOME Configuration

editor to configure various options of compiz