You can efficiently change the console fonts, character sets and keymaps through the following command:

sudo dpkg-reconfigure console-setup

The configuration is stored in the file /etc/default/console-setup, and can be edited by hand as well.

The changes are effective for all virtual consoles after reboot. To apply the change for the current console, run:

setupcon

To prevent changing the console font completely (i.e. native system/BIOS font will be used), set the font to "do not change".
The equivalent in the config file is:

FONTFACE=""
FONTSIZE=""