Updating other modules schema when creating custom module I need to add a information to a content types within my module. Generally, is it good practise to update node_type schema or is it better to create my own and join it to the node_type via primary key?

Thanks.
You should make use of the hook_schema_alter to update entity schema of existing schema's.

function YOURMODULE_schema_alter(&amp;$schema) {
  // Add field to existing schema.
  $schema['users']['fields']['timezone_id'] = array(
    'type' =&gt; 'int',
    'not null' =&gt; TRUE,
    'default' =&gt; 0,
    'description' =&gt; 'Per-user timezone configuration.',
  );
}