Install the freetype-freeworld package from rpmfusion.
Set the hinting on full
Reboot
There is no need to change the default fonts to the liberation set, that is a personal choice. After installing the freetype package and setting the hinting to full, the default sans fonts look a lot better anyway.
Greatly improved my font rendering by using the custom local.conf font configuration from the blog mentioned by sonoran.
Also, if you are running compiz, right click the Fusion icon and make sure that "indirect rendering" is checked. This has also improved my font rendering (with NVIDIA graphics card).