Constraining Your Keyword Research Based On Wrong Assumptions!
Do you ignore a keyword phrase simply because it appears to have low search count? Do you target only the keywords that have the so called high demand and low supply?
This is another very common mistake that is made for a variety of different reasons!
Concentrating only on high search volume keywords or keywords with low search result counts
In the early days of the Internet it was common for marketers to decide on the viability of targeting a specific keyword phrase by checking the search volume and then checking to see if the keyword phrase results in a large or small number of web pages when searched in Google (or any other search engine). Only keyword phrases with large search volumes (demand) and low search result counts (supply) were then used. This is termed Keyword Effectiveness Index (KEI for short).
This method has long since lost its appeal.

The concept of deciding if a keyword phrase has large supply based on the search result counts is not a good method anymore because the web is full of junk sites created using automated tools. Remember that the world wide web is also growing rapidly.
The viability of ranking high for a keyword phrase is mostly based on how many high quality web pages are ranked in the search engines. Even for keywords that have millions of search results, there may be only a handful of quality web pages in the search engine results. The rest will be made up of junk automated pages or Made For Google Adsense pages.
Even if Google shows 3 million search results for a keyword the actual relevant, displayed results are mostly less than a thousand!
You can easily verify this by scrolling through the Google search result pages. After a few pages you will see a message like...
"In order to show you the most relevant results, we have omitted some entries very similar to the 915 already displayed."
What this means is that, in many cases you can reach the top 30-50 places in search rankings with basic keyword optimization. The real competition comes after that. So, just high number of search engine results should never scare you off!
What is really important is a proper competition research and not a decision based on how many web pages are listed by a search engine in its search results!
Not considering Multi Word Keyword Phrases (Long Tail Keywords)
The web is so vast today that many times it is almost impossible to find anything useful by typing in a single keyword into a search engine. So people have learned to search better by typing in more combinations of words. Besides it is pointless to search for
car rental
when you require to rent a car in Seattle. A more appropriate query will be
car rental seattle
or
seattle auto rental
or
cheap seattle car rental
or
budget car rental seattle
and so on...
So if you optimize your site only for car rental your web page will be just one among the millions and you will find it very hard to obtain and maintain top search engine results. Instead, go for additional words that include the region (state, county, city) or any other possible words that your customer will type in.
In many instances it will be necessary to create additional keyword phrases by simply adding city names and or other words to existing keywords. You can easily do this using a software like Keyword-Pad or Keyword Strategy Studio.
Looking For Keywords Based On High PPC Costs
Do you only look for keywords that have very high PPC costs? The cost per click values are not always a good indication of anything. In many industries large companies simply set high cost per click values for generic terms. Remember that the indicated PPC costs are mostly the maximum they are willing to pay and not what they actually pay.
Forgetting Low Search Volume Keywords Used By the Experts and the Savvy
There are a number of keywords in every industry that are never popular enough (among the general population) to show up in regular keyword research tools. However these keywords may be used by the Internet savvy and expert users.
Always make sure that your web pages contain the relevant industry keywords and other lateral phrases. If your product or services cater to corporate or business clients this is even more important.