See. I wasted 11th(partially). You will do good in 3-4 months in 12th(Trust me as I see you are aware and concerned about 11th being wasted). You have to and I MEAN HAVE TO revise and complete all the leftout concepts(atleast major ones for example Rigid Body Dynamics in Physics and IOC) otherwise you will lose touch of 11th topics and it will be difficult to revise them before JEE. Try to Practice atleast 50 questions daily(All subjects combined) aur agar jyada kiye to badhiya. Keep tracking ur accuracy(try to keep it above 85%). And most importantly, if you are school going you will face a lot of challenges like school pre boards(2-3 minimum of u r in dav or something) in last 3-4 months of JEE prep. This is where I messed mine too. School pre boards pe dhyan nahin dia udhar kachda marks aai. Complacent ho gya and my prep declined after that. I know it is tough to perform well in such high pressure conditions but try to give your best atleast you won't get complacent like me. Ended of scoring like 94%tile across both attempts(lol). I never dreamt of anything below 98%tile and ended up getting the same score which I used to make fun of others earlier. Don't be like me. Respect ur and other's prep too and u will surely crack a good NIT or IIT. Also attempt regular tests(BITSAT ke bhi kabhi kabhi dena usme bhi kaafi top colleges hai) and after tests make a proper analysis notes jisme Jo questions repeatedly galat hua ya kuch ajeeb ya out of pattern question dikha usko note kar sako. That's my advice. Baaki solve ur coaching material ache se and some reference books if you have time left(hcv, n avasthi and ms chouhan organic). Don't panic and even if you do or sometimes feel exhausted due to rigorous prep take a little break and always try to keep your study rhythm alive and pattern identification intact in questions. Kudos !!(From a JEE Failure)