Overture, then google trend, then allintitle, then check competition, then check domain ... then check backlinks, then back to overture, mabbe wordtracker, rinse repeat and bam you got a good keyword phrase to optimize!
Another recomendation: powerful desktop keywords tool at www[dot]ibizresearch.com/mlb.html , for 100% FREE! No GIMMICKs!
Also remember to test it against Google Trends since you might have surprises. Overture shows you some words and some traffic. I always double check it with Google Trends
Aside from Overture Keyword Suggestion tool try this link. 'coz almost users are using the Overture and sometimes failed to give suggestions....
I used https://adwords.google.com/select/KeywordToolExternal Then http://inventory.overture.com And compare
Some basic explanation on finding useful keywords and key phrases of how search engines work: http://www.monash.com/spidap4.html