(1) Themes — frezr

Step 1: Themes

Choose the right theme. It's 2015. There are designers that have spent hours of work making stuff that is good looking and crossplatform. Why bother using anything else? Personally, I like using my own version of Numix called DarkArrow. The only real difference is Openbox and some modification to the GTK3 theme. This is what it looks like:

Or, you could use the light version of Numix, if you're not a fan of dark UI's, it also looks pretty nice:

How to get it:

if you want DarkArrow, do the following:

cd .themes
git clone https://github.com/gbdu/darkarrow.git

if you want Numix, and you're on Ubuntu or an Ubuntu derivative:

sudo add-apt-repository ppa:numix/ppa
sudo apt-get update
sudo apt-get install numix-gtk-theme numix-icon-theme-circle
sudo apt-get install numix-wallpaper-notd

How to install it:

There are several ways to tell GTK2 and GTK3 applications what theme to use. Personally. I use three different applications to get the job done:

sudo apt-get install lxappearance gnome-tweak-tool xfce4-setting-manager qtconfig-qt4

Launch lxappearance

This will make all GTK2 applications follow the new theme. But it won't theme GTK3 apps. You will need to use gnome-tweak-tool and xfce4-setting-manager's appearance for that. You'll be happy to see that Numix/Darkarrow will show up in all sorts of applications.

Run gnome-tweak-tool and qtconfig-qt4 to choose the theme for GTK3 and QT4 apps.