Login to Google Keyword Planner: https://adwords.google.com/KeywordPlanner
*You will need an AdWords account to sign up, but just create a dummy campaign then cancel it when you’re done.
Start with a broad phrase which will generate a larger number of keyword suggestions. Click “Get Ideas” then click the “keyword ideas” tab. Now scroll through keyword suggestions to find phrases you want to rank for.
A few basic tips:
-average monthly searches is estimated and only shows numbers for that EXACT keyword (not all it’s variations)
-competition is for AdWords, not SEO
-best practice is to select long-tail (very specific phrases) because there is less competition and it’s more specific, so higher conversion rates
-use the filters to narrow down your keyword suggestions (location and the “include” option are most helpful in my opinion)
-“chicago wedding photographer” and “wedding photogapher in chicago” are essentially the same keyword, so no need to select both
-write down all the different photography services (in this case) in a keyword list so you can create a new landing page for each service
I like to use Google Autcomplete AND Google Keyword Planner to make sure I don’t miss any keywords. You will likely find opportunities in both tools. Find Google Autocomplete tricks here: http://onlinemediamasters.com/4-google-autocomplete-tricks-for-finding-seo-keywords/
Full article: http://onlinemediamasters.com/using-google-keyword-planner-for-seo-keyword-research/