Hey 

If you are solely devoted to JIMPER entrance exam you should know it is a tough exam , the seats are less & you need  lot of patience & hard work to clear Jipmer entrance 

time is no limit if you want to clear a particular exam but you should keep more options open 

for this exam particularily : 

starting preparing now 

know the syllabus very well know the exam pattern you have to practice previous year questions for this exam ( mock tests are available on their site) 

Plan you preparation : do not get confused and refer to a lot of books 

identify key topics , set time table & summarise topics using charts & mind maps . 

Answer questions that you know first in the exam to gain confidence

English should be prepared from previous year question papers 

rest is all luck as to what is asked 

good luck!