1. Include an import statement in addon.xml:
   <import addon="script.module.kodibgcommon" version="1.0.0"/>

2. Import in addon.py (or other .py files)
   from kodibgcommon.utils import *

The settings objects allows easy access to addon settings as long as you know the setting's id.
Just call settings.id-of-the-setting
If you have a bool setting with id 'debug' i.e. <setting id="debug">true</setting>, calling settings.debug will return a boolean value of True or False.

if settings.debug:  
  execute_function()
else:  
  execute_another_function()  

if you have a setting holding a digit number i.e. <setting id="id">1234</setting>, calling setting.id will return 1234 as intiger.
Any other settings are considered strings.

if settings.id > 0:  
  execute_function(settings.id)
else:  
  execute_another_function()  

log(msg, level=xbmc.LOGDEBUG) - the function logs a message to Kodi.log file, prepending the addon id.
The message is visible only if addon's setting 'debug' is True.

get_addon() - returns the current addon instance
get_addon_id() - returns current addon id
get_addon_name() - returns current addon name
get_addon_version() - returns current addon version
get_profile_dir() - returns addon profile directory.
get_addon_dir() - returns addon install directory.
get_resources_dir() - returns addon resources directory.
get_lib_dir() - returns addon lib directory.
get_platform() - returns OS type - Android, Windows, Linux etc.
get_kodi_build() - returns current Kodi version and build number.
get_kodi_version() - returns current Kodi version i.e. 18.01
get_kodi_major_version() - returns Kodi major version i.e. 16, 17, 18 or above.
log_kodi_platform_version() - returns Kodi version and OS type.
get_unique_device_id() - returns an unique identifier by concatenating Kodi version, platform and uuid.
notify_error(message, duration=5000) - raises an error notification message in Kodi's top right corner.

get_params() - parses addon's URL and returns a dictionary of params.
make_url() - transforms a dictionary into an addon URL (prepends the addon plugin path).