We now have probably read a lot of topics or drills about draw and that many of us have acquired the knowledge on how to execute this shot properly (applying factors such as proper stroke, precise low CB hit, loose grip, levelled cue etc...). But how straight is your draw? Have you ever find yourself in a situation where you needed to have a straight draw in order to have a good position for the next ball but ended up having an angled-draw & gone out of shape?
I have that many experiences. So I have come up with my own practice-drill in trying to improve/achieve a straight draw myself.

DRILL SETUP:
As in the diagram, place 3 balls (e.g. 7, 8, & 9-ball) near the head-spot in between the 1st & 2nd diamond of the long-rail. Align 2 balls (8 & 9) perpendicular to the upper-corner pocket, the distance of the these two balls should be 2-ball width. Then place the 3rd ball (7-ball in this example) on point A within the straight line towards the corner pocket. Now place the CB on the same line (somewhere in the head spot).
Try to shoot & sink the 7-ball & draw the CB from it towards point D without nudging the 8 & 9 balls. Increase difficulty by placing the 7-ball further (points B & C) & also reducing 8 & 9-ball distance into 1 1/2 ball-width (or lesser as long as the CB can pass through).