What are class 12 CBSE board exam tips and suggestions?

first and most important tips is don't take tension and think of result before giving the exam. try to stay cool and calm. study and revise the topics. try to attempt the previous year question in the same way as you are giving your board exam. eats healty foods and try to avoid oily and junks foods. try to have a group of few student of same knowledge category and discuss different topics by the members so by this way also u can solve some of the doubts.... Best of Luck from my side... Be positive if u doesn't do enough well u can do better in the coming years. It's just the begining of your journey 

I will share with you my prepration which yielded me a good 80+ percentage.... firstly as soon as class 11 exams end, get to work. Probably in April or May. 

Get all the text books necessary. Buy them from the list provided by your college teachers, so that you don't have to re purchase texts used by your college faculty.

Do not buy guides. They destroy your prep. Stick to the text books. You can buy question banks instead of guides.

Start off during your holidays. Make a timetable

Keep it like how you would attend classes in school

Take breaks, do not go overboard with it. Do not tire yourselves.

I would take one chapter from each subject ie physics, chemistry and biology ( I didn't take maths as an option,I took up home science) per day and try to read it on day one multiple times.

In the second day and third I would read the chapter again and on the third day I would do the questions at the endof the chapter.

I would self assess. I never took tutions.

After which in the weekend I would revise the chapter.

I would keep 3 days for 1 chap each from the 3 subs and revise around 6 chapters on the weekends. I would keep a record to write down what I would read daily a dairy , and revise the entire thing in the end of the month. 

I would finish the text books by the end of December and start doing question papers and question banks from January and do a complete revision from Feb, also as in June when college started for class 12 I would do the assessments and would keep all the chapters I wouldn't understand for the teachers to teach me at college. I would also make it a point to do my records on time and attend practicals so i would not miss out on internal assessment marks. Vivas would be easier as I would have revised the materials a many times. 

Apart from theorems,formulas and a few material which needed memorizing, I would never mug up 

I would just read the same thing multiple times on and on and on until it stayed in my memory.

I hope it helps all of you, and do not stress over it ,stay healthy firstly stay safe , your life is more important than any exam , but make sure you make studies a priority.drink plenty of water and do take breaks.