Your instructor can advise on the order in which to take exams, but a suggested schedule might look something like the following.
1) Air Law, which is generally the first exam to be taken, before the first solo flight
2) Operational Procedures, as some of the subject material overlaps with Air Law and many of the study aids group the two subjects together
3) Human Performance, which is usually considered to be the easiest of the nine subjects
4) Communications, as you will also have been using the radio by this point and so much of the subject matter should be familiar even before you start revising. There is also some overlap with the Navigation exam
5) Navigation and Radio Aids, as your first solo flight is likely to be followed by an introduction to navigation in the cockpit and it makes sense to combine theoretical and practical learning as much as follows
6) Flight Performance and Planning. Along with Navigation, this is one of the more demanding exams and requires calculations to be made in the exam. Although some of the content overlaps with Navigation, we recommend taking the exam in a separate sitting because of its difficulty
7) Principles of Flight, which is largely about knowledge recall with only a few minor calculation elements
8) Meteorology, which is one of the larger subjects and therefore requires more reading and study
9) Aircraft (General) Knowledge. Similar to Principles of Flight, this is large a matter of recalling memorised information. However, it is on the easier end of the scale compared to the previous few exams.
Keep this spare in case of scheduling issues or difficulty finding enough study time to take exams in pairs. Sittings 2 and 3 in particularly are more demanding and if you're finding it difficult to learn enough material for two exams at once then you have this sitting as a safety valve
If you fail any exam then you will need to retake it. Retaking an exam requires a new sitting - even if you try to take the same exam within the ten day sitting window. You can incorporate retakes into later sitting so that if, for example, you were to fail Operational Procedures, then you could retake it in Sitting 2 along with Navigation and Communications.
Whether you follow the schedule above is entirely up to you and your instructor, but it should give you an idea of the kind of planning you need to do when you begin to study.
Next: The Air Law Exam >