@ abhishek 
yes , genrally every student does that , starting the jee prep in 12th class , but that will not very effective , maximum u can able to get a low rank iit , not more than that , and if luck supports , then something can happen . 
frst of all make a study time table . 
as u better knows which subject u are weak and strong , so, u can do yourself a time table . 
2- then just planned up for a week frst , donot going to plan for 2 -3 months right now beacuse short term planning are effective for long term prep . 
3- the next thing whatever u studied , donot try to forget that , whenever u getting time recap it . 
4- the next thing – at every wekend just evaluate your progress , and always give mock test on whatever topics u studied in every 4-5 days . 
5- donot ignore your sleep and recretional activity , these thing will keep your brain active . 
6- if u want then u can try askiitian self study course , they are effective format . 
ALL THE BEST ..
						

							
hello friend  
at very  first   put  ur  mobile and friends   side  
and 
then  start hard work   of studying  at least 9 hours per day 
first  focus on to complete  whole syllabus  
then  focus on that topics in which u have good command 
when u have small time  don waste on topics in which u find difficulties 
 start  with chemistry  it is easiest  subject 
give 3 hours  per day to each subject 
  take  video lectures  on you tube for  the topics   which u had missed    do more number of questions  
try probelums on  basic  then advanced   level 
  first start  ur studies with  ncert   
 
my best  wishes are with u 
  hope for ur good …........................................................................................................................................
THANKS 
AND 
 
 
PLEASE   ..... if    u   like  my  answer  and  my  answer   is  use  full    for  you  so please   just click on approve  button  ...and  if  you  have  any  other  question   or  dought     keep asking
KRISHNA BONDRIYA @@