Rather than just writing notes on the cards, one method I have sworn by since GCSE days is writing questions on one side of the card, and then answers on the other. This way you can constantly use the cards to test yourself about knowledge on the specification, and it really helps things to stick in your brain and be memorized.
I make them then go over them on the bus, at home, in class, anywhere really... its so easy.
I would'nt have gotten my GCSE or AS grades without them, the only subjects they dont really work for is maths (need practice not memorization) and English, and obviously practical subjects. but they work amazingly for most subjects.
I create a big stack of cards covering the whole specification for each exam, then once the material is memorised, you can use past papers to practice if its all gone in, or do posters/mind maps from memory.
good luck and hope this helps.