We often talk of dividing as being the reverse of multiplying, and indeed when dividing fractions this is the case. The way you divide fractions is very similar to the way fractions are multiplied with a simple twist in the middle.
Practice with worksheets. Once you have mastered the flash cards, try your hand at some worksheets. Start by practicing with one number set at a time. When you have mastered all of them, try worksheets that mix up all of the number sets and see how you do. If you know your tests will be timed in school, try practicing with a timer.