Custom Dimensions Code for Universal Analytics and Wordpress - wordpress

Question

Okay... this might be a long winded question but I'm sure it's a major issue that most wordpress site owners want to know about.
I've upgraded to Universal Analytics.
What I want to be able to do now is track traffic to my site according to the author of each post, the category of each post, and the tags that each post is tagged with.
In other words - show me data for all posts tagged "foo". In wordpress, all this information is already readily visible in meta tags on each page.
There is something called "Custom Dimensions" that seems to be designed for this. When you create a custom dimension in GA it gives you some code that looks like this:
var dimensionValue = 'SOME_DIMENSION_VALUE';
ga('set', 'dimension1', dimensionValue);
So...
Question #1 - Where does this code go? Google doesn't say! Is it supposed to go inside my existing GA code snippit? if so where?
Question #2 - Lets say I'm trying to track Authors. I'm guessing the code should look something like this:
var Author = 'Mr. Foo';
ga('set', 'dimension1', Author);
So the question is - how do I populate "Mr. Foo" with the actual author of the page? How do I tell Google to ignore this if there is no author (like if it's the front page?)
Question #3 - What happens when I try to track something like category or tag and a post might have dozens of tags?
Any help to solving this greatly appreciated! I've been on this for 2 days and have not found a single tutorial that even comes close. I swear I'll write one if someone can help me get this done...

Answer 1

Question #1: Place the code just before you call the 'send' command, like this
var Author = 'Mr. Foo';
ga('set', 'dimension1', Author);
ga('send', 'pageview');
You can also embed the Custom dimension in the pageview call as a parameter like this:
ga('send', 'pageview', {'dimension1': Author});
Question #2: You would need to use JavaScript to get the author data, check if it was not blank, and then to assign that value to your author variable. Do you have the author defined somewhere on the page identified with a CSS class or ID?
Question #3: Can you elaborate on this question and show what some likely examples and scenarios are?
Note that when using Custom Dimensions, you only have a total of 20 to work with (unless you are on Premium, in which case you have 200), so you will need to use them wisely.