When you sit down to study, the first thing to do is to keep a copy of your syllabus nearby. Post it on a bulletin board or paste it on the wall in front of you so you don't lose it. Your syllabus is going to be a guideline for all your studying. The British Council makes its exams exactly according to the syllabus. There are rarely questions out of syllabus, and if there are you will be compensated the marks for them later.
Go through the syllabus topic by topic. Make sure you know and understand every concept given. Cross reference with other books as well your course books. Your syllabus will not only tell you what you need to know, but it will eliminate the extra information in books. Memorize all of the formulas given.
A few months before your exam, get into the habit of studying every day. You don't have to sit down for hours at a stretch staring at your book. Start small, by choosing a topic to learn. Once you're done with the concepts of that topic given on the syllabus, start doing questions from past papers. These are usually available online or in book stores. Make a list of the topics you want to do the night before. Designate certain times to them, but don't overdue it. Keep small breaks in between. This will help you keep on track without getting over worked.
Simply reading from the book isn't enough. Practice everyday. The A-level physics exam has six exams. Each exam is different and you have to know how to attempt it. For each exam, there are certain key words the examiners expect you to know. Purchase past papers or find them on the Internet and practice as much as you can. Check your papers yourself or get them checked by a qualified teacher. If you aren't clear on a question, revise the topic from your books.
Students usually opt to only purchase the marking schemes, but its more beneficial to purchase both the marking scheme and examiner report. The examiners point out what they were expecting and the mistakes made by most of the students.
A-Level exams are distributed five to 10 minutes before you're allowed to start writing. When your time begins, skim through the entire paper before returning to the first question. Read it thrice before you begin. Calm yourself down and do not rush while writing the answer answer. Allocate time to each question. Look at one of the many clocks in the room (they will definitely be there because it is a part of British Council regulations for an examination center) after each question.
If you get stuck on a question, leave it be for the time being and move on. Come back to it later when you've completed the rest of the test. If you get stumped on the first part of a numerical question, don't worry. Even if the first answer is wrong you'll still get marks for the rest of the parts. Be sure you show all your working and state the formula you used. Once you're done with the exam reread everything you've written and recheck the numerical questions with your calculator.