The only ways I can think of of overcoming the fear of public speaking are using any one of these three techniques, or some combination of them: 1) do like Irena said and be prepared, be over-prepared. That takes the jitters away; 2) do a lot of public speaking. The more we do anything, the less anxiety-producing it becomes (I used to get nervous in the 90s trying cases in court, but I do it now and I don’t get nervous at all. It’s just that I’ve done it so much it’s no big deal to me anymore), and finally 3) go to your doctor and get a prescription for anti-anxiety pills. I know everyone is not going to like that suggestion, but they do work, so if your doctor will give you some they will help a lot. That’s about all you can do.
Toastmasters International is an organization devoted to one thing and one thing alone: helping people become better at public speaking. I recommend them highly. They do have chapters in India, but I don't know if there are any close enough to you. Unfortunately the Toastmasters website, http://www.toastmasters.org is down right now!
Toastmasters is basically a club. They have a structured set of lessons to work through. In a Toastmasters meeting, there are various activities that include having people give short speeches (e.g. 5 minutes) while other people watch them. The people are the "grammarian," who checks for English grammar and word usage; the "timer," who gives signals to let you know when your time is up; and, most important for me when I was in the club, the "ah counter," who counts the number of times you makes noises like "um" and "er" and "ah." It is all a peer group, learners helping learners. It is excellent.
Thanks, @Dan Toastmasters is close to my residence so I will check that out soon.
Thanks, @Irena. You are correct but what would you do if some overly smart people laugh at your silly grammar mistakes while you speak? I totally agree with you that after getting some positive response you could become more confident. Sometimes when people look at my face while I'm speaking it seems to me that they are eagerly waiting to make fun of me instead of correcting my mistake.