1) Start off with straight in shots, using the same distance between object ball and cue ball, same english offset and same speed and bridge length.
Once you are consistently keeping the cue ball, post contact with the object ball in the same line with the object ball and pocket, you then have the correct aiming adjustment for that distance/ speed and cue. Remember it (or write it down). There are several ways to track the adjustments. Here is a one from Dr. Dave (his whole FAQs on english is worthy of a read)
https://billiards.colostate.edu/resources/file/BHE-FHE_calibration.pdf
2) Change the speed and repeat.
3) Change the distance (add a diamond distance between cue ball and object ball) and repeat 1 and 2.
Writing down the adjustments at each diamond difference allows you to come back to the next practice session on the same table and have accurate results quicker.
Notes -
1) These adjustments will apply for a specific cue. Changing cues can make a big difference.
2) Table (cloth) and ball (clean, dirty) conditions have a small effect that you need to be aware of when using different ones.