Font Smoothing in Ubuntu

Step 1: Enable full auto-hinting:
Open a text editor (gedit) and paste the below code in it. Save the file as .fonts.conf in the home folder

<?xml version="1.0″ ?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<match target="font">
<edit name="autohint" mode="assign">
<bool>true</bool>
</edit>
</match>
</fontconfig>

Step 2: Set rendering/hinting for Gnome
System > Settings > Appearance > [Fonts tab]

Under the "Rendering" section, select "Subpixel smoothing (LCDs)".
Click the "Details" button.
Ensure your screen's DPI is set correctly (defaults to 96 dpi, but my screen is approximately 94 dpi)
Under the section "Smoothing", make sure "Subpixel (LCD)" is chosen.
Under the section "Hinting", make sure "Slight" is chosen.

Source