Hue.... the basics of laser training are fairly straightforward. At root, a laser from the ends of the club should always point to the targetline. To be 'truly' on plane, the pitch wouldn't change, although the actual 'pitch' of the plane can, and most often does, shift in a good swing.
I find that a laser on a heavy club, not hitting balls, in a dark room if possible, with a mirror, shows the plane to new golfers better than any description (other than Hogan's pane of glass, as a concept). Snead's wagon wheel, or Hale Irwin's 'trough' image can be good ones too.
A laser without a clubhead can be very effective, to start at least. Getting too caught up in the clubface before you can feel the 'swing' and the 'plane' can be counter productive.
I like to have people focus on that beam of light as if it were coming out of the hosel, and have them hit low pitch/punch shots with a 7 or 8 iron. It helps the takeaway tremendously. Gets people to 'feel' the 'one piece' motion (to about 8 o'clock).
The other image I like to use, is to have people become aware of the rotation of the toe 'above' that beam of light. The toe of the club must ALWAYS stay above that beam, or on it. Best to keep it 90 degrees from hip to hip, and the right wrist back/flat left feel is key to that.
The problem with the image is that students sometimes get their hands too far outside (too steep of a pitch), or inside (too shallow).
A great checkpoint (from Nick Price), is that at 9 o'clock, there should be a straight line from your hands, through your sternum, to the target. Get there, with the laser on the targetline, a flat left/bent right and let the club/body fall/rotate, hitting those short shots and letting your weight shift in synch with your chest/club/triangle. If you fail to shift (flow with the club), you may hit some fat/thin shots.
Once you can feel that position, you will start to feel that 'back of the left hand is the clubface' feeling, and the 'in synch' rotation of ALL of your body at/through impact.
The feel of your upper arms staying on your chest can also help, but don't overdo it too much or you'll be unable to 'flow' with the weight of the clubhead.