Start by making a list of every possible search term that people 
might use when searching for whatever you're selling. There's a good 
chance you'll easily come up with a list of twenty or so before you 
start to run out of ideas. That's the point at which you should resort 
to the following tips and tools that'll help you continue the 
brainstorming process of building your raw keyword list.
1.       Be specific
When selecting your keywords, you want to avoid stand-alone words that are too general. The Reasons are:
- You will face very stiff competition.
- general keywords are so broad they could apply to all kinds of products and services
2.       Think like a customer
Sometimes
 the difference between a company that succeeds and one that fails is 
simply a matter of talking to its customers and asking the right 
questions. Couple of things that should be considered:
Remember to keep the customer's perspective in mind.
Don't
 make the mistake of assuming you know what customers call your 
products. Do the necessary research to find out what keywords that 
customers are actually using to locate your products or services.
Learn to speak like your customers
Real
 people don't generally use insider terms of the trade when searching. 
So, unless you're selling to insiders within your own industry, you 
should avoid using industry trade terms. Think about words and phrases 
that real customers, not industry insiders, would use in a search.
3.       Collect Keywords from your Web site's Referral Logs
This
 is a very essential source of feedback regarding what keywords your 
site visitors are using to find you. Referrals coming from search 
engines will include the keyword query that a searcher used to find your
 site. People often search using some very creative search queries terms
 that you and your competitors might never think to optimize for.
4.       Check out Your Competition
Once
 you've acquired a small list (about 30 keywords), start entering those 
keywords into searches on 
Google and 
Bing. Scrutinize the Web pages that
 are coming up in the search results these are your competitors. 
Scouring their pages can help you uncover the keywords your competitors 
are actually targeting, some of which you may have overlooked.
You
 can also view the source code of your competitors' Web pages to 
determine what keywords they're optimizing for. If you are using 
Chrome then, in your browser's menu, click View, then Page Source. If you are a 
Firefox user, use 
Ctrl+U to view the source code. Once you see the source code, inspect the title tag which looks something like this:
<title>Baby Strollers – The best strollers and infant supplies for your baby</title>
Notice
 the keywords sandwiched between the start <title> and the end 
</title> tags. This title tag is where Web pages generally place 
their money making keywords.
5.       Cover All Your Keyword Variations
Next,
 look for variations on keywords you think might be successful. This 
includes misspellings, plurals, synonyms, merged words, or keywords 
separated-by-hyphens.
6.       Keyword Variations
a. Plurals and Synonyms
 - Many search engines utilize a process called word-stemming to 
identify plural versions of a keyword. In theory, this means that a 
search engine should recognize charity and charities as being the same 
keyword. In practice, however, the search results for singular and 
plural versions of a keyword are rarely ever the same. This means that 
you should optimize for both versions by working them into the visible 
text on your Web pages.
b. Merged and Hyphenated Words
 - Be aware that some keywords may be commonly merged or hyphenated. An 
example of a merged keyword would be webhost versus web host. In some 
cases, both the merged and unmerged versions will garner about an equal 
number of searches. In other cases, one will far outpace the other.
7.       Be Descriptive
Once
 you've covered all the variations of what you expect to be your most 
important keywords, begin adding descriptive terms to augment your 
existing terms.
 8.       Use Action Words
Try
 to recreate in your mind's eye how your typical customer conducts their
 various searches. It's likely that many will use action words in their 
searches.
9.       Target Local Markets
If your product or service is geographically relevant, then be SURE to mention the location in the text at every opportunity.