Backup your files first!!!!
In newpost.php & newreply.php -

find this:
Code
      $addtofav = "
         <input type=\"checkbox\" name=\"dofav\" value=\"1\" class=\"formboxes\" />
         {$ubbt_lang['ADDTOFAV']}
         <br /><br />
      ";

and change to this:
Code
      $addtofav = "
         <input type=\"checkbox\" checked=\"checked\" name=\"dofav\" value=\"1\" class=\"formboxes\" />
         {$ubbt_lang['ADDTOFAV']}
         <br /><br />
      ";

also Note - word of warning: This adds every post to the favorites by default. So the favorites database table could get large. Be warned of database bloat if your forum is active. <img src="https://www.ubbcentral.com/boards/images/graemlins/wink.gif" alt="" />

Joshua Pettit
Web Developer
www.ThreadsDev.net | www.JoshuaPettit.com