hey student

SOF is Science Olympiad foundation

IMO is indian math olympiad

class 11 syllabus consists of 4 sections-
1) Verbal and Non-Verbal Reasoning.
2) various syllabus you studied till class 11.
(Sets, Relations and Functions, Principle of Mathematical Induction, Logarithms, Complex Numbers & Quadratic Equations, Linear Inequations, Sequences and Series, Trigonometry, Straight Lines, Conic Sections, Permutations and Combinations, Binomial Theorem, Statistics, Mathematical Reasoning, Limits and Derivatives, Probability, Introduction to 3-D Geometry. )
3)Mathematical Reasoning and Quantitative Aptitude
4)Higher Order Thinking Skills (HOTS)

so the strategy is...............

be strong in class 11 math.

brother, there is no strategy. all you need is to be thorough in portions, solved at least 100 sample papers. solved at least 20 previous year papers. and some aptitude from normal book available in the market.

class 11 portions are really less. you could do this easily.

all the best

(P.S. i also have good rank in IMO. this is what i did)