Choosing the best keywords for your website is an art, blended with a bit of science. Making the right keyword selection is a balance between the number of people searching for a particular keyword and the competition for that keyword. The best strategy to understand this balance is utilizing keyword selector tools that help you discover how people are actually searching the Internet. By understanding how people are searching for your product or service, and how much competition you have, you’ll know what keywords to focus on and which to leave alone.
To start, a good technique is thinking of all the ways people could possibly refer to your product or service. Then, we’ll research these keywords (using a FREE keyword selector tool). This will reveal which keywords have the most potential for ranking in the search engines. Are you ready to find your best keywords? Watch the video below or go to YouTube to watch this SEO tutorial video on Choosing the Best Keywords
The Google Keyword Tool is probably the most important tool when it comes to choosing the best keywords for your website. The simple fact that Google dominates the search market, (because 8/10 searches are done using Google), means that this tool is pretty accurate at showing you how a large majority of people are using search. Here’s how to use it to get your best keywords.
The nice thing about this tool is that Google lists the search results for the specific keyword you entered at the top. Then underneath that, there is a list of many synonyms for that keyword. So if the keyword you typed in doesn’t have a lot of searches, you can see which ones do. For example, when doing this SEO tutorial, I first thought about using the keyword: "right keywords." The Google Keyword Tool research showed these results (NOTE: these results will change over time as people’s search patterns vary):

Only 480 searches for right keywords in the global search results. Those results span over a year of Google search and it’s search network. That may not be bad, but it’s not great either. Now look at this:

Best keywords had 9900 monthly searches in May and 8100 monthly searches on average over the last year. It doesn’t take a mathematician to understand that these results are much better than my first pick, over 20x better. So in this instance, using the best keywords may be a good keyword choice.
You may not want to rely completely on Google’s keyword selector tool, or maybe you just want to see how people are searching all over the web. In this case, you may want to look at another keyword selector tool called WordTracker. WordTracker compiles search results from Dogpile, which includes Yahoo, Bing, Google and other search engies. This gives you a different perspective on how people are using search across multiple search engines, and helps balance your research. You can use a limited version of WordTracker for free, or sign up for a seven day trial. After that, it’s $59/month. For most people, it’s not necessary, but this SEO tutorial wouldn’t be complete without mentioning it.
As we stated before, choosing the best keywords for your website is really an art. So it’s important to state that there are no hard set rules to choosing your keywords. When you look at the results from your keyword selector tool, you want to weigh the number of searches for a keyword against the competition you’ll likely encounter for that keyword. In short, more searches doesn’t mean a better keyword! If a keyword has 100,000 monthly searches, the competition for that keyword is probably fierce, and the chance of you ranking for it are far smaller than a keyword that is very specific and may only have a couple hundred to a few thousand searches monthly. Let’s look at an example of this in the next section: using long tail keywords.
Let’s say we decide to use "best keywords" as our keyword choice for this page. But we might also wonder if there is a more specific way to state our topic that people also search for. So we might look at "choosing the best keywords" as a keyword to focus this article on. That search may not have hundreds of searches, but "choosing keywords" does (as of the writing of this article anyway). If we title the page using this phrase, called a long tail keyword, then we narrow our focus, but keep the broader focus too, which is just "best keywords." In a sense, we’re covering our bases to include the short tail keyword within the long tail keyword. This maximizes our chances of being picked up for various searches people perform using these keywords.
Using long tail keywords is beneficial because a smaller number of searches for these keywords also means less competition, which also means it’s easier for you to get a higher search engine ranking for these terms.
Both extremes mean poor search results. When you do your research, remember that you don’t want keywords that no one searches, and you don’t want keywords that millions of people search. To improve your search engine ranking, you want to choose keywords that are in the middle–moderate search volume that suggests it’s worth your time investment to try to rank for those keywords, but not so much so that it will be impossible to rank for the keyword because of competition. In general, you may want to choose keywords that have at least a couple hundred search volume and 50,000 at most.
There’s nothing worse than creating a web page around a keyword only to discover no one’s searching for that keyword. Here are some other mistakes people make when choosing keywords for their website and how to avoid them:
Mutt Cutts of Google discusses the importance of keyword selection (short version) (Long version)
Aaron Wall of SEObook shows you the basics of SEO keyword research.