Presently I am studying in 9^th standard i want to know how to prepare for IITJEE entrance exam, as how to cover up whole syllabus at present what should be my stragey and plan.

Is coaching necessary for the preparation ?

You asking good question at this level. now you have good oppurtunity for future. 10, 11 and 12th class is play important role for future. Compition is tuff but if you start preparation form now you can get sucess.
for jee you should prepare 11 and 12 th subjects..
take in online examination which is related to jee and jee preparation.

Best of luck.