1. Clone the git repo
   

   git clone https://github.com/chenxiaolong/Debian-Packages.git
   cd Debian-Packages/

2. Install the build dependencies. Run the following command and install the packages it lists using apt-get/synaptic/etc.
   

   cd freetype-infinality/
   dpkg-checkbuilddeps
   cd ../fontconfig-infinality/
   dpkg-checkbuilddeps

3. Build the packages:
   

   cd ../freetype-infinality/
   ./build.sh
   cd ../fontconfig-infinality/
   ./build.sh

4. Install the deb files:
   

   cd ..
   sudo dpkg -i freetype-infinality/*.deb fontconfig-infinality/*.deb

You'll need to reboot after installing the deb files. Enjoy the better looking fonts!

Ref:

1. http://forums.debian.net/viewtopic.php?f=16&t=88545
2. http://www.webupd8.org/2013/06/better-font-rendering-in-linux-with.html