How To Add Field In Registration Page In user page, I want to add more field like username, contact number and address. What is the common way to do it?
You can either use Profile2, or you can add your fields in /admin/config/people/accounts/fields.

From Profile2 project page:


  Designed to be the successor of the core profile module, which is
  deprecated for Drupal 7. In
  contrast to the deprecated module this module provides a new,
  fieldable 'profile' entity - leverage the power of fields!


You can find out how to create profiles in Profile2 documentation