In the example below I have used a 50mm f/1.4 lens at f/1.8.  Pre focus on the eyes to ensure they are pin sharp, by moving your focus point accordingly.   The shallow depth of field will now soften all the other features not in the focus range , giving even more impact to the eyes.

To get a better view of how effective this is, here is a 100% crop of same shot

Hope this has been of some use. Have a go & let me know how you get on

(Read more Photography Tutorials here )