What sets them apart? I would not be able to comprehensively and categorically say that I know exactly what the difference, but I know they follow a few rules.

Rule 1.
Research your keywords. Rate your traffic. We must begin with a great selection of keywords and gradually fade to the most profitable and relevant. Say you promote widgets. You can not go waiting on 'widgets' keyword, as it is meant to have a lot of competition. What you can do is expand on, delving deeper. "Buy cheap blue widgets." You can not get a lot of searches, but you know that is very specific and is inexpensive.

Rule 2.
If you are selling something, be sure to eliminate those who are looking for free stuff. One way is to include a "free" in his campaign for virtually all the surfers in search of freedom and your keyword will not get to see your ad. It can also include the price in your ad. It is true that reduced rate of clicks, but you know that those who do click are more likely to convert.

Rule 3.
Include keywords in your ad. Say you bid on the sale of wigs of the word "big, hairy black wig." It would be prudent to include larger or black or furry wig. Best to include everything, because your keywords in your ad appears in bold and people related to relevance.

Rule 4.
Its title. Make a headline that draws attention to attract people to see your ad. Its head is the vital link if someone clicks on your ad or not. For some tips on how to write compelling headlines, you can download a free copy of my report.