One of the main reasons why students find it hard to score well in H1 Math is the lack of consistency. And that is mainly attributable to the idea that one should place lesser emphasis on H1 subjects as it is "not so important".
Prerequisite Knowledge
First things first  No Additional Math knowledge is required to do H1 Math. However, having background in A Math can help you do better in Pure Math topics. What you are already assumed to know, are E Math topics. They are as follows (nonexhaustive):

Quadratic Equations

Simultaneous Equations

Mensuration (Voliumes and Areas of Cones, Spheres, Cylinders)

Basic Coordinate Geometry

Algebraic Manipulation
Clueless or need a refresher? You may sign up for our Assumed Knowledge Express Track (AKET) Classes!
General Syllabus Outline
'A' Level Mathematics at H1 Level comprises of the following

Pure Math (40 marks)
 System of Linear Equations
 Quadratic Inequalities
 Indices and Logarithms
 Graphing Techniques
 Differentiation and Its Applications
 Integration and Its Applications

Statistics (60 marks)
 Probability and Permutation/Combination
 Binomial Distribution
 Normal Distribution
 Sampling
 Hypothesis Testing
 Correlation and Regression