Most of the patches can be downloaded from mirror sites as well as from the official WoW webpage. Because of the large number of patches we should cover how to retrieve them from mirrors, and how to manually split them.
Split Patches (PC)
1) Unzip the file to your Wow Directory and double click the updater to start the process.
2) Unzip the files to "C:\Program Files\World of Warcraft\WoW-2.2.3-to-2.3.0-enUS-patch" and double-click "C:\Program Files\World of Warcraft\WoW-2.2.3-to-2.3.0-enUS-patch\BNUpdate.exe
3) Unzip the files to "C:\Program Files\World of Warcraft\Patches" and double-click "C:\Program Files\World of Warcraft\Patches\BNUpdate.exe"
4) Unzip the files to "C:\Program Files\World of Warcraft" and double-click "C:\Program Files\World of Warcraft\BNUpdate.exe"

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Downloading:
To download more efficiently from mirror sites the first thing you need to do is check the description of the patch you are going to download. The mirrors are always listed in an ascendant order, but sometimes the order doesn’t apply to the language of the mirror, so if you are looking for a patch that is in Spanish you need to take care to check the description before downloading it.
Remove the www prefix before start downloading or any prefix related to the mirror url as it will help to go more quickly to the FTP folder. In case of any emergency use the reported site name as a parameter to help boosting the download; when you reach the FTP folder don’t use a booster or anything just try to minimize any other online activity during the download, but don’t worry the patches are really small in size and with today’s technologies the download will only take a couple of minutes.