The "dot Tune" method is well received by many photographers.
http://www.fredmiranda.com/forum/topic/1187247
However I got better results with Reikan software. This is not freeware, The standard version for lenses up to 400mm costs £20.
http://www.reikan.co.uk/focalweb/
There are other methods if you care to search for them.
Harry