Hello,
It is quite easy to study chemistry than the other subjects.Focus on ncert textbooks and read every line of it.Mark or note down the important points or formulas.Focus more on organic chemistry as this is the most scoring topic in any engineering entrance exam.First of all start with nomenclature and start practicing it.Solve reactions and note it down.Solve conversions as it is mostly asked.For inorganic chemistry you should only go through ncert books as language is quite easy and make notes also.For physical chemistry ncert is also best.Solve it's questions and make list of all formulas.
After all this,Solve mock tests and previous years questions to get knowledge about pattern and level of questions asked in entrance exams.
Good luck.