Step 1 study vocabulary of the textbooks in primary 5 to 6 daily, and revise weekly.
Step 2 Read up on all the good compositions and study their writing methods, then start to write something everyday.
Step 3 Study the scripts for all the topics for your oral examinations and read them out daily. try to take note of the important words and phrases in every topics. try to speak word in the scripts with relevant sentences naturally without hesitation.
Step 4 Ace the comprehension by reading stories and understand the plots and hidden agenda. read widely so that you get used to all kinds of expression and their hidden meaning. Then study the PSLE Comprehension questions and you will see they are mostly direct response questions and some higher order thinking questions. And learn to answer questions with relevant techniques.