If the focus of your PPC campaign is sales, you should consider adding "long tail" keyword phrases to your keyword list. "Long tail" keyword phrases are keyword phrases that are very specific, sometimes obscure terms, and often have three or more words in the keyword phrase. For example, a long tail keyword phrase in the category of running shoes might be a specific brand and product, such as the "Asics Gel 2010 running shoe".
While many of these "long tail" words might not receive as many impressions as a broader search term, like "running shoes", studies have shown that searchers using longer search phrases tend to be further along in buying cycle. The max CPC to achieve a high position with longer, more specific search terms also tends to be lower than that of highly popular, broad keyword phrases.
Keywords To Enhance Brand
If the goal of your PPC campaign is to enhance your brand, broad keyword terms might be best. While these terms tend to be more costly, there are definite branding benefits to associating your company with particular keywords.
Additionally, studies show that searchers believe that the company with the number one PPC ad position is a brand leader.
However, be careful when selecting these broad keywords. Broad keywords can also make your ad display for search terms that contain that broad keyword but are not relevant to your company focus. For instance, if you are a mattress company and you include the word "bed" as a keyword, your ad may also display for searches for "bed and breakfast", "dog bed", and "bed of roses".
This is where negative keywords come into play. Google allows you to input "negative" keywords in an ad group or campaign to ensure that these broad keywords, in combination with a less relevant keyword, will not display your ad. To enter a negative keyword in Google, simply put a negative sign in front of the keyword, like this: "-dog". In the bed example mentioned above, using the negative keyword "-dog" ensures that the ad will not display, even on the search term "bed", if the word "dog" is in the search phrase - ensuring that the ad will not display when a search for "dog bed" is performed.
In Conclusion
All in all, I tend to recommend a mix of both broad terms and long tail phrases, adjusting budget to provide a higher budget to one or the other, based on the client's PPC goals.
