I haven't contributed anything in a while so I figured I would write this up to help out some people new to playing on a Mac or playing in general who have a Mac without the need to go through installing windows through boot camp to play. I entered this over as a competition on another site originally but I'm probably not going to win so I figured I'd post it on here.
Getting Started
It is very important to make sure you are up to date with the latest version of OS X if you are playing on a Mac as many fixes implicated in the game are reliant upon having an up to date operating system in order to properly correct issues, as well as for certain features of the game such as graphics enhancements. For Leopard users make sure you are running on version 10.5.8 and for Snow Leopard Users 10.6.4. To check if you are running the latest version just go to the apple menu, then go to about this mac and it will tell you what version you are on. If you need to do any updates make sure you open the software update and let them install before installing the WoW client.
Properly Updated OS X
Installation
First things first you're going to need to either download the game from your Battle.Net account management page or put in your good old DVD/CDS you've got buried away somewhere! They're universal so that you can install the game on your Mac with them too! Just run the installer once it pops up and let it do what it needs to install so sit back and relax while it is installing and downloading the patches necessary!
Post-Installation
Assuming now that you've gotten the game all installed and patched up you can now start up the client and log in. It is recommended that you run in windowed mode because many times you will be multi-tasking and want to be able to easily switch windows or you can quickly hide the WoW window by pressing Command + H. This can easily be enabled through the settings in the game just make sure you select a resolution lower than your actual current screens if you wish to play in a true windowed environment.
Now you've got the login screen!
Inside The Game
If you are familiar with the Windows version of WoW you will notice the settings menu as well as the settings window will look a bit different one the Mac and have some different settings. It is recommended that you leave these settings on Fair and partial highs as I have done unless you are experienced with hardware, or are confident that the hardware in your Mac can handle going up to High or Ultra settings. Most Macs from 2008 or newer should be easily able to handle tweaking the settings up to ultra without experiencing too much of an FPS loss.
A non up to date OS X version will cause you to be locked from going over Fair on many options hence the red bars
Last Words
You should be all set to play now! Painful wasn't it? I sure hope not, with just a few steps you can be up and playing on your Mac in no time without the need of playing it on your old PC or going through the hassle of using Boot Camp on the mac. After all OS X is now a very friendly gaming operating system and is becoming a valuable market for game makers!
I hope this guide was able to help some new players or Mac gamers, or just provide some new information for those who may not have known some of this! I hope everyone enjoyed this little guide I put together.