I saw a question about keyword research recently where the questioner wanted to know how to find a more targetted keyword on which to base his domain name and articles.
Here's the response I offered:
Assuming you know what subject you want your blog to cover (weight loss in this example) you should find some high value keywords to target.
You want a keyword where there is a high demand but low supply. That means a high number of searches (demand) but a low number of results (supply).
So you need to do some quick research.
You can do this by coming up with a list of keywords for your subject and then typing them into Google. Check the number of results.
I've just typed 'weight loss' into Google and got 76,900,000 results. Typing in 'lose weight' returned 18,300,000 results - much better! (Less competition).
Then I suggest you go to Google's free keyword research tool, which you can find here.
The term 'weight loss' gets an average of 9,140,000 searches a month and 'lose weight' gets 2,740,000 searches a month - less than a third the number of searches that 'weight loss' gets.
But remember: there are 77,000,000 results for 'weight loss' but only 18,300,000 results for 'lose weight'.
The ratio of results to searches for 'weight loss' is 8.41. For 'lose weight' it's 6.6.
Therefore 'Lose Weight' is a more valuable keyword for you because there's a lower number of results to searches.
Or, put another way, there is a better supply/demand ratio for 'Lose weight' than there is for 'weight loss'
That's a very quick exercise to illustrate the point, and it took me about 10 minutes. You need to do some more detailed research so you can find a really valuable keyword - one where your ratio of results to searches is as low as possible.
Once you've found your keyword you can use it in the domain name you set up for your blog.
You can also use it in the tags, categories and headlines of your posts.
There's no reason at all not to use other related keywords as well - in fact, you should. Just position your primary keyword first, followed by the others.