Set up a list of relevant keyword phrases. Ask friends and colleagues what query they would enter when looking for a service or product like yours. Do not trust your own instincts in this!
Then try to find relevant synonyms by using a thesaurus, and take variations of English into consideration ("baggage" or "luggage," "optimization" or "optimisation").
Finally, go to one of the
online keyword services and see how popular the various search phrases are. The keyword services will also help you finding other relevant phrases.
We highly recommend the online
Wordtracker service for this kind of work.
Why you should settle for only one keyword phrase? You should not! However, you must find one keyword phrase that is to be the crucial one. Optimize your home page for that keyword phrase, as many search engines give more weight to the home page in the top directory (e.g. yoursite.com/index.html) than other pages.
You may try to optimize the same page for more than one keyword phrase, but under no circumstance should you go for more than three. If you do so, you will dilute the effect of the individual keyword phrases.