Game design

IIFA offers 3-year full-time course B.Sc in Game Designing and Development. The course has 6 semesters where the student gets introduced to the world of Game Designing with concepts of drawing. Institute offering a unique and comprehensive Bharathiar University degree syllabus and prepares a student for the fundamentals which is essentially required in today's industry. This well-blended syllabus in combination with communications and self-development classes makes IIFA students a preferred choice among leading studios and entertainment companies. The course is beneficial for students to explore drawing as a process of seeing, developing technical skills, and engaging in the use of drawing media as materials for communication. Students will learn how to identify, create and manipulate core game elements such as game philosophy, design process, player objectives, rule systems and the human elements in a game. The course eligibility criteria is as under:-
The minimum qualification is required to apply is 10+2 examination passed in Science/Commerce/Arts from ICSC/CBSE or any other equivalent board. So you are eligible for the above course.
Best of Luck.

The UG Game Design and Development at ICAT is a full-time program. It is perfectly-balanced curriculum of Game Art, Design and Development helps students in seeking a vast career, be it as 3D Game Artist, Level Designer or Plugin/Tool Developer.
Eligibility for B.Sc: Students seeking admission in ICAT for B.Sc program should have an educational level equivalent to a pass in high school (10 + 2 years of schooling). This includes those who have completed 3 years of Diploma from a recognized University or Government after completing 10th Std.
Further admission for Under Graduate programs is based on Aptitude Test and Personal Interview.
So, from above there is no barrier of class 12th marks for admission for B.Sc programs and requires only simply passing marks.
Best of Luck.

People might talk all about passion and hard-work, but some other things that matter are getting real. Other answers have advice on what language to learn or what book to read, but I will give you some real world advice.
There are three most common pathways to enter the game industry: as a programmer, as an artist, or as a tester. I wouldn't really recommend the third route.
1. Get a degree
The first step is to get a four-year degree. If you're interested in programming, get a Computer Science Engineering degree. If you're interested in art, get a degree in Fine Arts. If you are into writing, get a degree in English / Literature. (Some other distant options are starting out as a game writer, for which a degree in mass media / journalism can help. ). Do not go for diplomas / degrees in animation / game design. They are usually expensive and generally not worth the money that you put in.
2. Intern during summers
The best way to learn fast is by joining a small game studio or company that is looking for interns. It can be a great experience. Or do your own game project during the summer. Gather up some teammates brainstorm and start prototyping an idea. Or go solo and build a game during a weekend.
3. Connect with people & attend conferences
The best way you can socialize with people in the gaming community is by being a part of gaming related forums on the internet and attending conferences. Watch out for local game dev meetups in your city. Announcements for such meetups are usually made NASSCOM Gaming Forum. Some conferences that will be of interest are:
NASSCOM Game Developers Conference (Pune, November each year)
Casual Connect Asia (Singapore, May each year).