I'm in class 12. I don't know how to study C++ in computer science. What are some good suggestions or guides which I can refer to?

If you are science student then it will be the easiest subject for you. Don't panic if you can't find logic. I was scared of this subject but got 96 out of 100. It is really easy, read throughly Sumita Arora book only. The subject is somehow logical therefore Guides are never preffered by students. Try to grasp the logic and practice it on regularly basis.

Install a compiler (and possible IDE) . A compiler is required to because the actual source code need to be compiled into a file that your computer can run. After the successful installation of the compiler start practicing some basic programs like a program to find whether the number is prime or not , printing patterns , string code , arrays  etc.
practicing above programs will make you understand the execution of the code.
There is a lot of stuff available online which you can use to learn better .
For logic improvement the only trick is "spend a good amount of time with the problem and think of it's logic". If then also you are unable to hit the logic then simply google it. At starting thinking of logic may take a long time . But as you will move forward things will be easy to understand . Don't be in a hurry , learning things takes time.

I have completed my class 12 syllabus and now I want to study optics and electricity. What book can you suggest me which will help me for that and does not require higher level than class 12 to understand?

For optics best suited book for Class 12 is GRB and for Electricity I will recommend a practice book like Arihant Publications Chaterwise Physics or Xam Idea. has 2 volumes.The topics which you want to study-Electricity and Optics are in Volume 2.The book has a lot of solved examples and the solutions of the practice problems are given in the same book itself.This book will really help you to strengthen your concepts in Physics and you will really enjoy while solving the book.

I am in class 12th now. How should I prepare to do good in Boards?

12 board preparation just requires focus and concentration, I can suggest you good books for CBSE 12 preparation:

• Physics:- solve examples and read theory of NCERT Physics, for last 10 years questions Chapterwise Physics- Arihant Publication, for better understanding of topics refer the theory part of HC Verma- Part II, for theory plus numerical and a good overview of whatever you have learned go for Xam Idea- XII, for the real exam practice do solve the question papers of last 5-6 years of All India and Compartment. Compartment papers need a good labor and it will also clear most of your concepts.
• Chemistry:- you need to clear all the concepts of NCERT book and for better understanding of topics and visual impacts refer the videos of Xam Fear https://www.youtube.com/user/ExamFearVideos, Chapterwise Chemistry- Arihant should be practiced on regular basis. This will surely help you in scoring 95+ in Chemistry. For organic part learn the mechanism of all the named reactions as this will fix your almost 15 marks.
• Maths:- Solve the whole NCERT textbook for minimal twice and don't go for RD Sharma and RS Aggarwal. After you solve each chapter's NCERT start solving the real questions from Xam Idea- XII, it has a great collection of questions purely on CBSE scheme whereas RD and RS are not particularly for CBSE.
• English:- For English you should read the Flamingo and Snapshot books thoroughly and exceed your speed, Xam Idea- XII has a great collection of topics to write and read for boards prepration.
• Biology:- Contact my friend Aman Goel(9521752234), He scored a perfect 100 in CBSE 2015 in Biology.

Will the maths paper of CBSE class 12th be tougher next year (2017) like it was this year as the pattern has changed or will it be a little bit easier as compared to this year?

This time(2017) it is expected to be a great fall in level of question paper because it depends on the destiny of batch and 2016 students have been highly screwed up at that part therefore have suffered the same in Class X(2014) also.

What I will suggest is to be prepared on your part as you have immense time , ask your mentors to give you better understanding of the topics like Integration as it was the most time consuming for 2016 students.

CBSE has not given any leniency to the students this year rather the passing marks were decreased from 33 to 23.

Class XII Maths paper was almost predictable for every year this you could understand if you see last 10 years question paper. So students are always taught to understand the basics and practice them only till the level CBSE has been following from years but this time the paper came out to be  the most unpredictable one. This was only the reason there were complaints against CBSE on almost every online forums.

But in 2017 you can not make any excuse against the tough paper, because it could also be that CBSE is changing the pattern of Maths paper and 2015 was the first year to be served and coming year may have more tough papers comparatively to 2016 one.

Also consider this:

• This time JEE Mains & Advance were also tough.
• AIPMT paper was leaked.
• English paper was lengthy.
• Physics was time consuming too.
• Economics and Business papers were also out of league.

I am not trying to prove you that CBSE 2017 is going to be more tougher than 2016, but just convincing you to prepare hard.

I'm in class 12. I don't know how to study C++ in computer science. What are some good suggestions or guides which I can refer to?

If you are science student then it will be the easiest subject for you. Don't panic if you can't find logic. I was scared of this subject but got 96 out of 100. It is really easy, read throughly Sumita Arora book only. The subject is somehow logical therefore Guides are never preffered by students. Try to grasp the logic and practice it on regularly basis.

I have completed my class 12 syllabus and now I want to study optics and electricity. What book can you suggest me which will help me for that and does not require higher level than class 12 to understand?

For optics best suited book for Class 12 is GRB and for Electricity I will recommend a practice book like Arihant Publications Chaterwise Physics or Xam Idea.