So, one drawback of using windows managers instead of fully featured desktop managers is that when you are on WM, you have to do few things on your own.
In Arch, there are no font rendering patches. If you install a desktop environment, it handles this stuff by itself.
On openbox, I was getting very ugly fonts due to no font rendering. I looked up the ArchWiki which is a very good source but unfortunately I was not satisfied with the results.
While searching on forums, someone suggested to install ubuntu patched versions of some packages. So, these are the packages that you have to install for getting perfect font rendering. No other settings required.
fontconfig-ubuntu 2.8.0-1 freetype2-ubuntu 2.4.6-1 libxft-ubuntu 2.2.0-1
I would also recommend you to install ttf-mac-fonts & ttf-ms-fonts too.
Also, remove these packages if you installed them (related post)
pacman -R xorg-fonts-75dpi xorg-fonts-100dpi
To make Java Swing apps look nice, add this to your ~/.bashrc
export _JAVA_OPTIONS="-Dswing.aatext=true -Dawt.useSystemAAFontSettings=on -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel"