Chemistry is one of the main subject in your 11th-12th classes and is divided in organic, inorganic and physical chemistry. You can follow the below guidelines for your preparation:

• You should start with preparing a time table. Create a study plan.
• Make sure you include short breaks in between so that your routine doesn't become hectic for you. Study in short chunks.  
• Keep distractions away like cellphone, favorite serials etc.
• Find out your productive time, the time you study with high alertness.

Some of the important chapters in Chemistry are:

• Alcohols, Phenols and Ethers and Aldehydes, Ketones and Carboxylic Acids are the most important and have a higher weightage of questions in Organic chemistry.
• Coordination Compounds and p-Block elements in Inorganic Chemistry.
• Chapters like Surface Chemistry, Solutions, Electrochemistry and Chemical Kinetics are important in Physical chemistry.

So plan accordingly and do not forget to attempt mock cbse papers before you conclude your preparation.

Good Luck.