How do you make your theme Child Theme-able? [duplicate]

Few things have already been discussed here I would like to add more

In order to make your theme a good parent you also need to consider in following things:

• make your functions and classes pluggable ie, wrap your theme functions with
  function_exists wrapper so that they can be overridden in child
  pages.

  if ( ! function_exists( 'theme_entry_date' ) ) :
  function theme_entry_date(){...}
  endif;
  

• provide action and filter hooks generously