I would like to have registration and login page for my clients.by defining user and password and selecting their city. Now I using Theme My Login plugin for registration, but I want to do this without using plugins? Is it possible? If yes how Can I do this?
So you want a registration page for your site where they input their username, email, password, and city? If I'm understanding you correctly, do it like this:
I haven't used the Wordpress version, but it seems like it should be similar to the Drupal one - I create a profile in CiviCRM: http://www.yourdomain.com/civicrm/admin/uf/group?reset=1
In the settings for it, I choose it to be used for user registration and view/edit account. Username, email, and password you don't have to add to the profile because those are the minimum required elements for a user account.
Then any field you add there will be added to the registration page as well as their user account page (so they can view and update the information).
UPDATE: Forgot one step - you will need to enable an option in WordPress for the option to show up under profiles: Turn on "anyone can register" under Settings > General.
You can do this through a profile. Under advanced settings in the profile setup there is an option for WordPress account creation. You can make it required or optional. You will need to check the box 'Anyone can register' in the WordPress general settings and set a default role. This will insert the account creation fields into the profile if the user is not logged in. You can use this profile as part of an event registration, contribution page or insert the profile in 'add' mode with a short code on a WordPress page.
I would recommend installing a plugin that requires a reCaptcha when user accounts are created. This will prevent robots from creating junk users in your system.
Hope this helps.