Dear Anders,
Try putting with only your left arm, taking care to coordinate the motion of the left shoulder with the putter head in the thru-stroke, so that the left shoulder does not stall out before the stroke is completed but continues upward in the thru-stroke vertically away from the ground. The left armpit should not open much if any in the thru-stroke.
Then, after some of this, add the right hand onto the putter but only very casually, without engaging the right hand in holding or gripping the handle, but with the right hand only passively accompanying the left hand and arm.
Finally, focus on keeping the throat line and middle of the body from shifting across the midline of the stroke (as defined at setup by the leading edge of the putter face) during the thru-stroke in the direction of the target. That is, stay back behind this midline with the upper torso once the putter head reaches the bottom of the stroke going forward.
At the end of the day you should end up having a conscious awareness (during practice, but none especially during play) of the left shoulder and the throat area being the main body parts involved in the stroke.
You can also practice along a baseboard of a wall by setting the putter toe close to the baseboard and then making strokes the hew close to the wall without hitting the wall in the thru-stroke.
Cheers!
Geoff Mangum
Putting Coach and Theorist
Offering Free Podcast Tips for Putting Every Friday on
GolfSmarterTips.com.
The best putting instruction book in golf history is now available for purchase in hardback or as an immediate ebook download:
Optimal Putting: Brain Science, Instincts, and the Four Skills of Putting (2008, 282-pages)
Geoff Mangum's
PuttingZone
PuttingZone Clinics
Flatstick Forum
PuttingZone Channel on YouTube
PuttingZone Picasweb Image Gallery
Golf's most advanced and comprehensive putting instruction -- you're either in the PuttingZone, or not.
Over 2.5 million visits -- 200,000 monthly from 50+ countries -- and growing strong.