How to update wordpress new version?

I am using wordpress old version. I want to update new one.

Can you tell me how to update new version. So, my old files and database never get an effect?

 

Here is the official instruction:
http://codex.wordpress.org/Upgrading_WordPress

You might also want to give a Wordpress Automatic upgrade plugin a try

 

Thanx for info..

 

Yeah +1 vote for the auto update plug in, makes life easier.

 

If you want to do it manually. Deactivate your plugins, delete wp-includes/wp-admin folders and all Wordpress root files except wp-config.php as this file contains your database info. Then upload the new folders and files and launch your blog URL and add .../wp-admin/upgrade.php Click through until you get a "successful upgrade" message.

 

I don't know which files should be backup? and how I can do successfully

 

If you log into your webhost cpanel there is an icon "Backups". Click on it and you will be able to download a backup of your home directory and your WP MySQL database.