Add extra fields to Joomla registration forms

I need to add some extra field to Joomla registration form without using any extension. Please does anyone know how I can go about. I have created the extra fields in the db and added the html 开发者_如何学Pythonfor the textfields but I don't know what to do next.

Some articles here that describe how to add extra fields:

http://joomla-and-more.com/2010/02/05/how-to-velden-toevoegen-bij-de-joomla-registration-form/

http://blog.manchumahara.com/2010/03/18/how-to-add-extra-fields-in-joomla-registration/

http://www.youtube.com/watch?v=dk_86nHu3AM