Hi Falak, The best thing you can do to increase your weight is -- simply eat, and have proper diet on time, you should not miss your breakfast also, and have a heavy breakfast. Apart from this you can do exercise for few minutes per day, which will increase your apatite and you'll eat more. Eat high calorie, high protein diet. Do not increase the intake of junk foods and greasy foods, this will contain unhealthy fats. Have eggs for breakfast. Custard is good for putting on weight. Hopefully this will help!

One of my friends had tried using the Gym protein drink. Something called as MegaMass, which the regular gym goers use after the exercise.It comes in Vanilla and Strawberry flavors.I have seen lean and thin young biys and girls getting benefitted by it.

So to summarize:

1. Gym protein

2. Eat a lot of milk based products like Custard and Milk shakes (flavored milk).

Good luck.