Efficient work is purposeful work. You cannot work purposefully without a plan. A clear plan allows you to work towards your ultimate goal, rather than aimlessly hopping from one task to the next. In the words of a famous poet:
A goal without a plan is just a wish.
Planning your work should not be a complicated affair. The best plans are simple and flexible. Simple, flexible plans are easier to follow and less likely to fall apart. You don't want to waste any time or energy trying to stick to a complicated plan. You want to put that time and energy towards the real work that needs doing. Your priorities will keep changing during the study period and unexpected events always occur. This means that the best plan is one which can be adapted as necessary.
Before you zoom in on the small details, consider the big picture. You need to have a rough idea of what you will be doing between now and when you take your exams. This is your Grand Plan.
For any Grand Plan, you should establish the following information:
You should spend some serious time thinking about these questions. It will save you a lot more time and effort later on. This information doesn't have to be exact, since a lot of it won't become clear until you have spent some time studying. These questions will depend a lot on your individual situation, so you will have to use your own judgement when answering them.
The most effective grand plan is very simple: complete all of the available past exam papers. Work backwards from your exam dates. Plan which days you will complete each past paper. Review and learn from your mistakes in the remaining time. This is exactly what I did.
Create a timeline (or get a calendar) and sketch your activities from now until your final exam. As your preparation progresses, you will be able to build on your initial sketch. Your Grand Plan will become more detailed as you gain more clarity over what needs to be done. Remember: this is an ongoing process. Don't expect perfection straight away.
You should be able to create a daily plan in five minutes. Military-grade timetables are not necessary. A daily plan simply ensures that when you have finished a piece of work, you immediately know which work to do next. Just like with your grand plan, you should sketch your daily plans long in advance. Don't make them too detailed or rigid because your priorities will keep changing. When the day approaches, you will have a better idea of what needs to be done and you can create a solid plan.
Your daily plans can be goal-based or time-based. A very easy goal-based daily plan could be to spend the day working through a whole subject or topic from start to finish. When you have finished the subject or topic, you have finished for the day. The plan should also include how you are going to work. For example, will you be working through past papers or writing notes?
A time-based daily plan could be to study for 6 hours and then stop. The problem with this approach is that it is hard to predict how much progress you will make in a given period of time. This then makes it very difficult to align time-based daily plans to your Grand Plan. Furthermore, time-based plans provide you with little incentive to work efficiently. An hour of inefficient work is treated no differently to an hour of efficient work. Goal-based plans reward efficiency because you can stop working as soon as you reach your goal.
The best daily plans are therefore primarily goal-based, perhaps with some time-based elements for activities like eating, exercise, or other commitments.