The quality with which the forms are practiced has a major influence on the ability to apply the WT principles in actual combat.
The sequence of movements in the relatively short WingTsun forms is quickly learned, but even masters constantly refine their execution.
Naturally one could discuss countless aspects to which particular attention must be paid when practicing the forms, but the object of this series is not an exhaustive analysis of all the movements in a form. Instead Dai-Sifu Schembri provides examples of important aspects which should be noted.

Chum-Kiu

Part 1 – 1st half:

After adopting the stance, the crossed Gan-Sao (Gau-Cha Gan-Sao) is performed. The arms are then brought to the crossed Tan-Sao position (Gau-Cha Tan-Sao) with an inner rotation (Kwan-Sao). The arms are then  returned to their initial position (Sao-Kuen).
After performing a punch on each side, as in the 1st form, both hands are placed in front of the chest and thrust upwards as an explosive movement (Chuen-Kiu).
There is then a turn to the left while bending the arms, the left above the right. This is followed by a turn to the right, then back to the left.
Both arms are then stretched forward with the palms downward. The left forearm forming a Tan-Sao is struck with the right palm, then the right forearm with the left palm. This sequence is repeated twice more.
The right palm is thrust forward (Ching-Cheung) while the left hand adopts the Wu-Sao position. After performing this three times, there is a turn to the right while bending the arm to form Lan-Sao. A crossed Tan-Sao is then performed in front the chest, followed by a forward turn with Bong-Sao. This sequence is repeated twice more.
After the last Lan-Sao movement, a punch is executed over the right forearm with the right arm. The first section is concluded with a turn to the starting position and a Fak-Sao to the left. The whole sequence is repeated on the other side.

NOTE:
When performing the Bong-Wu movement, make sure that the Wu is not withdrawn. It is erected where it is, and remains there. The Bong-Sao is in front of the body. The arms are not moved during the turn.

A detailed description of the Chum-Kiu form with numerous photos may be found in “Chum-Kiu of the WingTsun System“ by Grandmaster Leung Ting.