Instructions
Go to the "World of Warcraft" Realm Status website linked to in the Resources.
Search for the realm that you play "World of Warcraft" in, and determine the status of the server. If the server status is busy, then your latency issues may be the result of server side problems that you can do nothing about.
Turn off any custom UI mods that you have installed into "World of Warcraft." These mods often take up large amounts of your Internet connection's bandwidth, which can significantly increase your latency.
Log-in to your character in "World of Warcraft," and press the "Esc" button.
Select "Options" and then "Network" from the game menu.
Uncheck the box that says "Optimize Network for Speed." Doing this can resolve some types of latency issues.
Install the most up-to-date drivers for your computer's network card.
Configure your Internet connection's router to allow "World of Warcraft" to make connections. If your router has a firewall, or bandwidth restrictions, this can cause your latency to increase.
Close any programs that are using your Internet bandwidth on all of the computers connected to your home network. Programs that use large amounts of bandwidth, such as downloads or streaming video, can cause your latency with the "World of Warcraft" servers to increase.