I haven't finished my degree yet, but I finished my first year (10% of the degree, which is environmental science) with 79.5%. I started out going about things the same way as A Level and scraped low 2.1's. But then by employing the following techniques I managed to pull my grades up into strong firsts.
1) If you're lucky enough to have lots of friends on your course, collaborate. Obviously copying is a massive no-no, but if you help each other out then it helps. For example, in my group of friends, we had people who were strong at different parts, whether it was chemistry, maths, geology, genetics or economics. By helping and supporting each other, it helped us to clarify anything we weren't sure of and make sure no one felt "inferior". Obviously, if you're completely stuck in the mud, there's no harm in asking a lecturer or consulting a book for clarification, but helping your friends always helps.
2) Read, read, read! Don't go overboard, but if you feel like you could do with a bit more knowledge, go for it.
3) Be sure that when you're finding sources, they're reputable. Don't settle for anything just because it's loosely relevant.
4) Read the question several times. Make sure you understand what they want of you.
5) Before answering a question, make a plan (I'm being a hypocrite here... there were a few all nighters, including two on the same night. Please don't do it. Even though I got over 80% in both of them, it's not good, and you'll be recovering for days as well as spotting silly mistakes when you get your script back when it's been marked that might've not appeared had you done it while relaxed and awake!). You don't have to 100% stick to the plan, but it's recommended so you know where you're going with the assignment and don't repeat yourself/miss out key issues. Find good references and use them.
6) Read your work as you're going through. Does it make sense? Does it flow nicely? Is the grammar correct, and is your spelling top notch? Read it over and over again until you're bored of it. Then give it to a friend or two to read to make sure you're okay. Poor writing will lose you marks! Same goes for a calculation-based assignment. (One of the assignments on the double all nighter was a calculation one. All my calculations were perfect until the last few questions. Although I got ECA awarded, I still chucked away about 5-7% because I didn't check properly- again, another reason to not pull all-nighters because you're going to be too tired to check them correctly!)
7) Have a life as well! Being locked in the library 24/7 is as bad as not studying at all, if not worse, because you stand the risk of crashing your brain. Get the balance right.
8) Look after yourself. Eat well, sleep well, take time to exercise.