Shoulder weak point training is about developing your shoulders if they are a weak point in your physique. To do this, adjust your training so that you do more sets and more exercises for shoulders, and use as many of the Shocking Principles as possible to work that area with maximum intensity.
Schwarzenegger likes to use the Stripping Method for shoulders. With dumbbells, you start with heavy weights and move on down the rack; with Machine Presses or Cable Laterals, you just keep moving the pin one plate lighter each set.
Another way of accelerating deltoid development is by supersetting Presses and Raises, for example, a Barbell Press followed by Front Dumbbell Raises (or Upright Rows) in order to completely blitz the front delts. For a really intense delt workout, try doing a 3-Pump Set: Presses, Front Dumbbell Raises, and Upright Rows. But be prepared to bear the pain.
To get the best results from Raises, remember two things:
1) Keep your palm turned downward throughout the movement; or, even better, turn the hand a little farther so that the little finger is higher than the thumb (like pouring water out of a pitcher). This helps isolate the deltoids and make them fully contract during movement.
2) Be as strict as possible. Raise the weight without any cheating, and lower it fully under control. The stricter you are, the more intense the effect on the deltoids.
Another way of increasing the intensity of your deltoid training is, after each set of Dumbbell Raises, go over to the rack, take a heavier set of weights, and just lift them out to the side as far as possible and hold them there as long as you can. This "isometric lateral" will help fully exhaust the deltoids and bring out maximum striations.
As a way of getting extra development in the rear deltoids, Schwarzenegger used to leave a light dumbbell, usually 20 pounds, under his bed and, first thing in the morning, would do 5 sets of Lying Side Laterals with each hand without stopping. However, he never counted this as part of his regular shoulder workout. He also did a 2-Pump Set, starting with facedown Incline Lateral Raises and, when he was too tired to continue the set, he changed to a kind of Dumbbell Rowing motion to fully exhaust the rear delts.