There are numerous keyword tools available for purchase or a subscription fee but one of the most reliable is still the free tool built into Google’s Adwords system.
Log into your adwords account and choose ‘Opportunities’, then on the left hand side ‘Keyword tool’
Type the main keyword or phrase for your niche, then using the advanced search tool choose your geographic area for the data to be pulled. Also set the minimum search volume to a number that is reasonable.
Click search to show the results and then sort by competition from the lowest to the highest.
Use the keywords listed in both the title of your blog post or web page and also variations of it sprinkled through your article.
Lastly, check your web site stats from time to time to see what phrases people are typing in to find you. Use those phrases for article or blog post titles.