Give your Ad Unit a descriptive name so that you know where it is located exactly. The name can only contain letters, numbers, underscore and hyphens. No spaces allowed.
As an example for a descriptive naming of Ad Units this is one Ad Unit I use:
PatFra = Acronym for the website
LR = Large Rectangle
1P-Threads = Ad is located inside the first post of a thread in my forum
First_Aid = The Ad Unit only shows in my subforum with threads about “First Aid”
This way you have all the important information about your Ad Unit combined in the Ad Unit name so you know exactly what kind of Ad Unit it is and where
it is located. (I explained my naming strategy in more detail here: The Secret to using Channels)
Now enter a description for your Ad Unit.
Then select the size of your Ad Unit e.g. 336x280px if it is a large rectangle.
The target window option defines the behavior of the Ad after a user clicked on it.
_top = the advertised website opens in the same window
_blank = the advertised website opens in a new window
Ok let’s continue.
Below the Target Window option you find the placement option. If you already have placements and want your Ad Unit to be part of one or more placements you can select them now. But don’t worry, you can always add them later too.
The next option is AdSense inventory settings.
I explain how to use this Option for displaying AdSense on your website with DFP here (recommended version): How to set up Google AdSense using DFP Small Business build in AdSense option
You can also set up AdSense as separate Line Items and Creatives which I explain here: How to set up Google AdSense as Line Item using DFP Small Business
Now click on save and you created your first Ad Unit.
The Page looks like this (if maximize revenue was selected):
Continue to create as many Ad Units as you have on your website(s).
After you have finished creating all Ad Units for your website you need to implement them into your website.
Click on the Inventory Tab and then on Generate tags on the left
Select all the Ad Units that appear on your website for which you want to implement the Ad Units. After you selected all Ad Units for your website click on Generate tags at the bottom.
First you need to click on the drop down menu (1) and select Google Publisher Tag (asynchronous). For more information about the new Google Publisher Tag read: DFP goes asynchronous with its new Google Publisher Tag. Time to switch
You then get a HTML implementation example where to put your DFP Ad Server Tags into your websites HTML.
Now your website is set up to serve Ads via your new DFP Small Business AdServer.