It is very important to understand that when you put any type of english/side on the cue-ball, the direction of the cue-ball will no longer travel straight.
Practice the following drills to increase your understanding of how english effects your aim and how the cue-ball will travel after making contact.
Note: To make sure that you are getting the correct cue-ball curving effects, make sure to test out the same shot 5 or 6 times exactly the same way with the same speed and see how the results differ.