Practice, practice, practice.
Do not accept the bare minimum timescale for graduation if you are not very confident and competent to go diving unsupervised afterwards.
Most agencies mandate ‘performance driven training’ – meaning that your mastery of skills should be fluid, comfortable and consistently reliable. You shouldn’t progress at each stage until that level is reached. That is a standard that diving instructors are bound to adhere to (but, sadly, many don’t).
Don’t let dive instructors rush you through training.
You paid for training, not just to be handed a worthless card. Make sure you’re properly trained to be a safe and confident diver from day #1.
Instructors who focus only on “fun” should work in a clown circus, not be training people to dive safely and be able to survive things going wrong underwater.