Adding Separate Chat windows in WoW:
The main 'General' chat window can become convoluted with all the messages appearing in one window, so you can create separate chat windows and name them the specific chat type that you want to appear in that particular window i.e. Say, Yell, Guild, Whisper, Party, etc.

Then you set ONLY that type of chat message 'on' for that particular window, so only those messages appear there (i.e. unclick the message type you DON'T want to appear there, as the default is to have everything show).

To do this:
-Right-click the 'General' chat tab
-From the pop-up menu, choose "Create New Window"
-Then right click on the new window's tab
-From the pop-up menu choose 'Channels' then set only the chat value/type you want to appear there (Ex: for a 'Party' window you would CHECK 'Party' AND UNCHECK 'Say', 'Yell', 'Guild', 'Whisper', etc.)

So now you would have extra tabs in your chat area and can click on them to see the messages separated in their respective windows.

The only drawback you may notice w/ making a new chat window is that you have to switch back and forth between tabs often if you wish to view General chat for trades or general information. But since you DO still have the General tab to go to for all messages, what you can do is I keep General on most of the time and just switch to a specific tab to see if you have missed any of that type of message.

Moving/ReSizing Chat Windows:

Another possibility is that you can also pull the specific window onto a new part of the screen. (Just drag it, using the "drag-n-drop" method: click on the tab itself, keep it clicked and then move it to where you want it to be. It will detach itself from the main window.)

For example, normally there are 2 chat windows:
-General and Combat

You can pull the combat chat window to the right hand side instead of it being underneath the General tab (so now you have 2 chat windows at the same time, the one on the left = "General" and the one on the right = "Combat"). So now you can see both chats at the same time.

You can also shrink a given window to only show a few lines OR make it bigger to see like a page in a book depending on your preference. (Click on the window "frame" itself, then drag to the size you want it to be.)

It's all a matter of preference, you can leave them together if you prefer.

Inserting Item and Quest Info in Chat:

-Linking Items for Sale

If you are buying or selling an item, you should link the item to your chat message so that prospective buyers can see the item for sale. To do that, open your chat prompt, type your message, and then link the item by holding down the shift key and clicking on the item from your bag slot. The item will appear in brackets and color coded for the item’s rarity. Other players that see the linked item in chat can click on it to open up the item’s info box.

-Inserting Quest Names into Chat

You can also do this somewhat with Quest names. Open your chat prompt, type your message, and then insert the Quest name by holding down the shift key and clicking on the Quest name in your Quest log. The Quest name will appear in the chat and the other players will see the exact name of the quest you were talking about. This avoids mispelling and speeds up your displaying of the name to them, to see if they have it.