@ jayadhir
stochiometry is the besic concept of chemistry , mainly as far as competetive exams are concerned , then they will ask u the ques from mole concept , calculating the concentration terms like normality , molarity , molality , mole fraction , etc .
even jee can have combine ques from volume composition and mole fraction ,
so, u need to practice enough ques to get mastry over that .
u no need any type of shrtcut fro that , just apply the formula , do the conversion if required and then find out the answer .
and mainly the n1v1= n2v2 formula thats the most imp one as far as jee mains is concerned .
IF U HAVE DOUBT IN ANY SPECIFIC TOPIC , THEN LET ME KNOW
ALL THE BEST ..