Best thing I can suggest is to consciously look at someone in their eyes as you are talking. Practice this at every opportunity you can get, be it the cashier at a store, friends or whatever, just be non-threatening with the rest of your body.
It will take time for you to break old habits, so just practice as much as you can.
There's a great topic about body language here: alpha-body-language-video-series-vt1394 ... highlight=
(I recommend you watch the full series as it's very informative but, Episode 3 and Episode 9 are of particular use to you)
*credit goes to poeticlyskuac*
When people talk they tend to direct their eyes away occasionally from the person they are actually talking to, but ensure you try maintain eye contact when they are responding to you as this sub communicates interest in what the other person is saying.
Best way to describe this, without coming across as just a blank stare, is to focus on just one of their eyes and alternate the gaze to the other eye every few seconds.
Practice with a friend, as you'll not be able to practice in a mirror, another great thing to try is use a webcam, the lag creates enough of a time lapse to notice your reactions - You'll see the eye movement is very subtle but noticeable.
Hope this helps
