From one who did it long, long ago .. and used to teach it ..
(a) get a good grounding in the basics .. a few texts around .. Worthington is as good as any
(b) the courses available (and I am out of touch these days) probably will emphasise the exams, and that's useful once (a) is addressed .. lots of past/sample papers gets the focus from (a) to the exam
(c) absolute imperative .. make yourself a schedule of mins/question to spread the time allocation according to the marks on offer .. no point in getting the first three questions done perfectly and leaving the rest not attempted ... and then, stick to the schedule .. if you haven't finished the question, leave it, go onto the next one .. and then come back at the end if you have some spare time ...