Well, i recommand manual checking only if you know that you are in the top 30-40 positions. Otherwise, it's not worthy. Though, if you do it manually, be sure to log out from your google account and start private browsing, as only this method will show your the exact results.
There are some keyword ranking tools available on tool that can search google for your targted keywords. One such tool is available from seobooks.com website also
Get free seo Feedback : like i remember it will tell you the place up to page 100. interesting tool. http://www.seoscheduler.com/ reply how it's working or if you know some "smart" tools