Why is it that some people can remember things really easily and others can't?
well it could be that they have a better memory, but that doesn't mean that you can't improve your own memory when it comes to revising.
Some people seem to just read over their notes and that's it, done, I've remembered it. Others can read over their notes 6 or 7 times and still not remember it a couple of days later. This is not because they have a bad memory, they're just revising the wrong way for them.
Memory is connected to your senses, that''s why you might be reminded of a certain event when you smell or hear or see something. When revising you can take advantage of this by using multiple senses when learning something, making the memory a lot stronger
So here is the ideal way of revising. Use as many parts of your brain as possible when revising. The most concise way of doing this is by reading a line of your notes once or twice, close your eyes and imagine it in your head, then write it down whilst saying it as you write. This way your brain is using 4 different brain areas at the same time.
Now if this seems a little extreme then at least try one of them. Try rewriting your notes, or reading them out loud. If you have a strong imagination, you can also try making a mind map and remembering the locations of the information on the map. The more brain areas you can use during revision, the more connections between that memory and the rest of your brain will be made. You may find that one way of revising is much more effective than others, it's best to experiment to see which method is most effective and try to incorporate it into your revision.
Revising for a specific exam type: Memory is very context dependant. So say you have an oral exam, the best way to revise would be by speaking out loud, as when you speak during your exam it opens the same neural pathways as when you were revising, so you'll remember better, so say you have to write a timed essay, it's best to write out your notes etc etc.
You should also try to time your revision with when your exam is, as again you're more likely to remember something when your internal environment (in this case your body clock) when you're learning is the same as when you're remembering it.
Essentially what you should do is try to make your emotions, needs (hunger, thirst), body clock when you're revising the same as when you have your exam.
And finally, take regular breaks when revising, not long breaks but say take a 5-10 minute break every 20-40 minutes, this way your brain has a chance to rest and you can consolidate what you've learnt. Try lying down closing your eyes during your break and try to recall what you just went through. If you can remember at least the gist then you're going at the right pace, if not then you're going too fast as you aren't converting the short term memories to long term memories, they've been pushed out of your head by the new information coming in. Which is another reason why you should take regular breaks.
A good way of testing how well you understand a subject is explaining it to someone else. If you know the subject well enough to explain it to someone else, even a pet will do, then you understand the subject at a high level.
The best advice I can give is don't leave it all to the last minute, you can never start revising too early, the sooner the better. I generally start properly revising about a month before the exam but any later than that and you're starting to rush it. If you haven't started revising 2 weeks before a big exam then might struggle if you have multiple exams.
Follow these tips and hopefully you'll get the results that you want. Best of Luck!!