Lots of wordpress user are stuck when upgrading the blog. As for me, i’ve see lots of technique or tutorial about wordpress upgrading but not meet or satisfied my needs. So here it is i want to share a complete step-by-step complete with snap shot to make guide more easier.
Before i go further, i must explain that there is lots of plugins out there to upgrade your wordpress. I don’t want to review it one by one (may be in the future) right now. Plugins that i use was wordpress-automatic-upgrade by techie-buzz.co (Contributors: keithdsouza, ronalfy) Here we go:
*I assume that you already download it and upload to your plugins directory.
Here is what WPAU does:
*Click image to better visuality
01. If installation cannot access you directory, it ask for authentication. If you trust them why not you enter you authentication.
02. Backs up the files and makes available a link to download it.
03. Backs up the database and makes available a link to download it.
04. Downloads the latest wordpress files from http://wordpress.org/latest.zip and unzips it.
05. Puts the site in maintenance mode.
06. De-activates all active plugins and remembers it.
07. Upgrades wordpress files.
08. Gives you a link that will open in a new window to upgrade installation.
09. Successful Upgraded
10. If you blog no need to upgrade.
11. Re-activates the plugins.
12. Cleaning backup files. Make some free space on you storage.

*Update
I was go through all this process and there is no error. if you use my method and found error post it here or you may direct you question to plugin’s author as i talk about above,techie-buzz.co (Contributors: keithdsouza, ronalfy) .
I was tested this to latest wordpress engine 2.3.3
You may also want to know how to backup wordpress blog