Hi pallaviisinha,
Co-ordinate Geometry ('graphing' questions) are not that common on Test Day - you'll probably see just 1-2 in total, so that category is not a big 'point gainer.' Most of the rules involved in graphing questions are fairly standard rules (graphing points and lines, slope, parallel/perpendicular, etc.), so you might just need a resource that will simplify all of the concepts for you and give you enough practice to be comfortable with the variations.
What resources have you been studying with so far?
What is your goal score?
When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich