It's never too late to revise.
Your college give you mock exams so you can see how well are you doing. They are also a good way to give you a wake up call.
First of all, goes through your mock papers and see where your struggling. These's are the topics you need to revise the most.
Secondly, revise these topics. I did AS maths, biology and chemistry. In maths I revised by doing past papers. That's the only way you can revise for maths tbh. For chemistry, revise the content and then practise questions. Same for biology. There are great resources online for biology and chemistry.
Thirdly, every time you do a question that you get wrong; highlight it and try again after revising the topic area.
Revision cards are good for definition that come up in biology and chemistry.
From my experience, all 3 maths mocks I did I got an A. However, biology and chemistry, I got Cs so that was my wake up call to sort out those two subjects.
If you need any more help or have more questions, feel free to message me. Don't stress yourself out and good luck!
Posted from TSR Mobile