I've been using rxvt-unicode (urxvt) since the Openbox days. I like it because it's lightweight and highly configurable. Best of all, it's Desktop Environment independent, unlike Konsole for KDE and GNOME Terminal for GNOME.
When I switched the distro from Slackware to Gentoo on my main workstation, I revisited its configuration and started fiddling. I learned quite a lot of things that I didn't know how to do or cared about back then.
The information in this site is the result of my researches in the Internet and of my experiences. This information below is solely used for my purpose and may not be suitable for others.
Configuration of urxvt is done through ~/.Xresources. The details of the file can be referenced in Arch wiki.
I didn't know this but you can include sub files for different applications in this file, like you'd do in many programming files.
# cat ~/.Xresources
...But, I have the config only for urxvt so I didn't want to do this.
I used to have problems setting fonts properly in urxvt and it was a tedious process. When I updated the file, I logged out and back in to see the changes reflected because I didn't know other ways to let the changes have effect. But it's no more. There is a way to load the file without logging out/in.
# xrdb ~/.Xresources
That's it. If there is an error in .Xresources, it'll mention in its output though messages can be sometime cryptic.
Also, there is a way to test if specified font(s) is correct by running the following command:
# urxvt -fn "xft:Inconsolata:size=13"
This opens up a new urxvt terminal with specified font type and size. That's how I test a font before I put it in the config file.