ICSE ,right ? 
The general pattern of the question will be followed: a composition, a letter, an unseen passage followed by grammer.
The grammer consists of :(i) fill in with APPROPRIATE form of verb
                                              (ii)fill in with prepositions
                                              (iii) join the sentences without and,but,so
                                              (IV) Do as directed
(i) you need to make sure that you maintain the Tense of the passage.If you start with present , you got to end with present (unless there is a flashback or something like that in the passage).

(ii) "Practice makes a man perfect". Yes, practice. Some words have fixed prepositions and u have to use them. Any change in them word change the meaning of the sentence , and ultimately you would be losing MARKS. So learn those Prepositions .MARK my WORDS ...-->LEARN them.Practice and correct usage in Spoken english would surely help your CAUSE.

(iii) joining sentences won't be a tough task, but remember not to use "and , but or so"  anywhere in your sentences.

(iv)Even this part is mark scoring, just follow the instructions in the bracket and make proper sentences.

BEST OF LUCK FOR YOUR BOARDS