Normally, as a higher level student u should focus on HL topics especially in calculus, they always bring integration by parts or substitution In at least one section A, and beware: they aren't as simple as they seem u have to perfect your skills since u mostly need to becomfortable with every trick (like e^x cos x integral for instance) and also differential equations!!!! Those are extremely important. In addition , u probably want to learn implicit differentiation very well. This year, they brought a hefty question on "rate of change" from the applications of differential equations, so again i suggest doing ALL the examples in this part pf the book and acing the chain rule. Regarding trigonometry, for HL i have done many past papers, but i normally found that they bring NOTHING but mensuration, which requires a sort Of innate understanding of shapes and angles and an ability to detect shapes within shapes, if i please. Normally u are required to find an expression for a paeticular angle in a figure and pf course u must know ALL the identities and how to apply them. Trigonometric proofs are also frequetly asked in HL exams and they are merged into calculus problems (u will often use the double identity angles in integration) so know them very well, also, although not present in the book i have seen them ask arc tan and tan identiies so google them and learn them complex numbers are a paper 1 favorite and require algebraic skills so i suggest u to learn the concepts very well and then just practice practice practice. Since thwy usually ask for proofs. Also practice Argand diagrams, as they are just free points in the exam. Regarding vectors, again try to put emphasis on the HL topics, that is, 3D geometry. I mean u rarely see them brig anything non-plane related sp u should understand intersections of planes and lines, u should be a ninja at cross AND dot product, and also be comfortable with other subtleties like angle between planes and so forth. I really want to add one point to underscOre it, practice all the examples for calculus, it's the only way you will learn all the tricks for integration, like cos^2x, tan x, and the one i mentioned before. Once u know the trick, it is a piece of cake , Good luck!