* Targeted -> Show your ad to the right people
* Visiblity -> Your ad must stand out
* Descriptive -> Your ad must accurately describe your offer
* Content -> The actual offer should appeal to your visitor
* Motivating -> Your ad should incite the visitor to act
In my experience, several of these do not always mix well. For example, it is hard to stand out when you try to sell the same widget as those 12 other advertisers. Quite often, the price of your widget will be the same as those of other merchants / advertisers, as will be its terms of delivery etc. So by including all these (relevant) bits, you are prone to 'drowning in the crowd' again.
How do you cope with this? Which ad factors do you give priority?
What is it that defines good ad copy
I would say that context defines the right choice of ad copy.
There are several contexts to consider, but perhaps the most important are:
The competition. Meet or exceed their strengths and/or capitalise on their weaknesses. It's unlikely that you're the only ad. Try to use factors that other advertisers have overlooked. If the listings are price-driven consider making this a point of difference, or just undercut on price.
Perhaps most important is the audience context: who is your ad for?
If you're selling high-end graphics cards to a small percentage of gamers, they're much more likely to read the text in ads. It's less important to stand out than to address their specific technical requirements (I think you defined this as descriptive). If you're selling budget laptops then you might want to concentrate on standing out with low prices and free delivery.
Different industries and even different keywords might require a different approach. It may be that you can't intuitively pick the right ad copy, but it is straightforward to test different approaches and measure the results. You could even run ads with a clear focus on each of the factors you mentioned and see what works best.
Even without a large sample size you could relatively quickly identify the factors that worked best against your competition and for your audience, and make ads combining the most succecssful aspects.
However, my first point of call is usually to bid extremely high get number one position and build some good history to keep my advert there.
Another selling point that is often overlooked by your competitors is targeting local markets.
So if you're selling laptops, you can use several regionalized campaigns to target London, Manchester, Birmingham, etc.
So that each advert would say
"Laptops from London (or manchester, or birmingham, etc.)
Laptops from your Local Experts.
Visit Us Today."
This kind of targeting can work really well, especially with expensive products because there is some kind of integritery to be gained from being local, it's also convinient for the searcher to use a company based near them.
In the same category for "looks"...I also try variations of upper case lower case or written like a sentence and various punctuation or characters to see what performs the best.
There's really no golden rule. I've found that ad strategies that work well in one industry don't work at all in another industry.
