Doing keyword research is an art. It is amazing the amount of money Internet Marketers spend on keyword research tools. If you have no money to invest in keyword research, then take advantage of the free tools that are on offer. Look no further than the Google Keyword tool.
Type in the main keyword into the Google keyword tool and take a close look at the results generated by the tool. You want to ideally pick a keyword that has decent search volume with mild competition. The ideal daily keyword searches should be at least 50 -100 searches a day and more importantly, you want to check the competition online for that particular keyword.
Ideally you want the number of competing pages to be under 50,000. Some say that even 50,000 is high, but anything lower than 50,000 can be a reasonable target for getting into the first page of Google with some hard work.
Another angle to take is to look at the long tail keywords or product keywords. These products may have very low search volume but they can be easy targets for top rankings in Google within a day or two. Moreover these keywords also bring in ultra targeted visitors to your site who are more likely to convert better.
Also don't forget to look for jargon terms or industry specific terms used in your market that you may not be aware of. These keywords can be golden because these are the keywords that need some creative thinking and work. So most likely your competition may ignore it, since they may have not have taken the time and effort to do research.
Having powerful keyword tools can be a big help because there are tools like Market Samurai, Keyword Elite etc that can show you keywords that you should go after and how easy it is to rank for the respective keywords.
