Most amateurs I teach have a tendency to move their head during their putting stroke.
Try this indoor drill:
Place your head in the door way and assume your putting stance. Next make several strokes while keeping your head against the door frame. If you feel your head wanting to move it probably is on the course resulting in pulls and pushes.
Learn to keep your head still by making strokes in the doorway without your head moving. If necessary turn around and place your tailbone in the door jam and make additional strokes. The less your body moves the more face control your putter will have in relation to your target line.
Conquer this drill and watch your putting improve dramatically.