How to solve qustions of Electrostatics . I know th formula but not able to solve problems

@ sourabh 
In electrostatics u have to assume some complicated thing , so, for solving the problem , u need some assumption power like the presence of charge in a cylinder etc . 
and if u knws the formula and cannot solve the problem , then its happening with most of the student . 
the reason is that – either u are putting the formula in wrong form or not able to convert the units . 
REMEMBER – units are very very imp in phy . 
so, u need to be carefull enough for that . 
and learn and apply the correct form of formula , as in the case of charge distribution , we have diffrent cases – linear , surface , etc . 
and mostly , ques will be asked from coulombs law , config of capacitors , dielectrics , and gauss law . 
PREPARE THESE AREA THROUGHLY . 
AND KINDLY LET ME KNOW IN WHICH QUESTION U ARE FACING PROBLEM . 
SO, THAT I CAN HELP YOU WITH THAT .. 
ALL THE BEST ..