Properly Settings one's language environment and font in Emacs (in Linux)

Two important defaults:

Language environment to UTF

Font

Are these set through init.el, as in:

(set-language-environment 'utf-8)

No!

For UTF add this line to .bashrc

export LANG=en_US.UTF-8

For font, set the default font through .Xresources

Emacs.font: Hack-13

If on Windows, add this to dot emacs:

(set-frame-font "Cascadia Code 28" nil t)