I've been asked this a few times now, and since I've finished 2/3 of my mid-semester exams, I'll give you a brief (or detailed, however you want to put it) overview of my routine. I'm actually quite versatile in my style of study in that I can adapt my brain to many styles but it just takes a bit of time to become accustomed to all the different methods.
But I maintain the fact that I can never purely read through something and absorb everything; I get maybe 5-10% of it. Visually, my brain can't really process things from first glance. Even after 5 or so times, I'll have a lot of trouble remembering. I need other ways to embed things in my brain. I'm certainly not a visual person; from greatest to worst learning styles, the other is definitely kinaesthetic -> audio -> visual.
Kinaesthetic is really being active in your learning by doing things to learn, but I need a combination of all three. Firstly, I'll read through my lecture notes, or if you have high school notes - then those, to see what's relevant. Of course I'm not going to understand what I'm reading, but at least I can recognise the content when I read it in the textbook. That's the next step - reading through the textbook. I really need to grasp a concept and understand it fully before I can take the bits and pieces I need for my exams. It's a lot more work I know, but at least it's a way that I can understand. I mean, I'd much, much rather understand absolutely everything and beyond than to skim through something and remember nothing.
After reading the relevant sections in the textbook once, I read over it again and match what I'd read in my notes to those corresponding in the textbook. Then, I take very short notes (not really, I write a LOT just because at this stage, I'm not completely sure what's relevant and what's not) in my notebook and make sure I understand those notes. The key is UNDERSTANDING - you can memorise things later. That's the easy part; if you can understand something, memorising just takes time but you grasp the concept.
If I need a better understanding, I search around for videos until I find ones I can understand. That might take a few hours, but it really consolidates my understanding because it mixes my visual reading with the audio recording on the video while demonstrating another visual aspect - the picture from the video. Of course, I take video notes from them and it helps a LOT because those little notes trigger important segments that replay in my head - my mind works that way.
After that's all done, I type up my notes and organise them into one single document. That way, I have an accumulation of everything that is essential to learn for the exam. There's no time wasted in flipping from page to page, book to book and trying to learn something you don't understand. By typing up your notes, you're obviously learning when you read your notes and process them into sentences you understand. And that's just it - what you're typing are hopefully your own words - and not some textbook's. If you really understand what you've spent all that time on, you should be able to explain those concepts to anyone, or at least understand what you're trying to convey with them. Organising your notes is definitely the key to remembering.
I test myself by revealing the key words of each concept and covering the content part and trying to revise that. Retell yourself and even talk about it with your family members. I think that's the bulk of my understanding - when I can discuss what I've learned with my dad. It's so useful to have someone of a medical background in the family because they understand 100% what you're learning; it's great. They test you and if you can answer every question properly, then you've learned.
Other things I find useful are flash cards - they're pretty much the same as notes, except they're a lot bulkier in terms of shape to thickness ratio and a lot more effort to prepare. I find them extremely useful, but it's just that the amount of content I have to learn means that I spend hours and hours actually preparing the cards and then more time cutting them up and it's just counterproductive. Another thing is group study. Definitely useful - VERY useful. Here, you can discuss your extent of understanding and compare it with the different points of interest with other people. If someone doesn't understand something, then you can teach your strong points and that REALLY consolidates your knowledge. Conversely, if there are things that you perhaps are not as good at, people can do the same thing. One thing I suggest though, it's a waste of everyone's time if you go there without knowing ANYTHING. Study beforehand before discussing it.
And yeah, there you have it: Michelle's comprehensive study guide.