Guys, I have been trying to gain some weight for a long time. But, its not happening. I have tried the protein n vitamin stuffs from a lot of places, but no result. 
Have you guys tried anything and got result out of it?? 
What should I do guys, help me out.

Are u looking to gain muscles or r u just concerned about your overall weight? To gain muscles (and hence weight), increase your intake of protein (meat, beans, lentils, egg, whey protein etc) and carbohydrate (rice, flour, bread etc). Workout 5 days a week concentrating more on strength/weight training rather than cardio exercises like running. Try not to eat too much salt or processed meat. Also, don't eat too much sugar and eat real fruits instead of fruit juice. I hope this helps!

 mega mass ..from GNC

 PILOT, do you mean the 13 days' diet with 4 scoops of that protein shake everyday? 
I have done that too with the workout schedule as said.. hehe... 

lol this sound funny but ye it's truth i went to Nepal for 3months and my aim was to get some weight so i can get back to weight training again  this is what i did every evening Local Raksi ra bhutun and few other items we find in our so called "Raksi Bhatti" better then many so-claimed best restaurant i was only 58kg when i left for nepal when i came back to us couldn't believe 80 :P

Now after few months of Weight training everything is in balance still at 75kg :P Drinking does increases your weight but if you can control and keep upto balanced level with weight trainings you will like it .

In that case increase your Reps and train with more Weights!! It takes 2500-3000 Calories to maintain weight (www.caloriecontrol.org/healthy-weight-tool-kit/weight-maintenance-calculator-men), so do Increase your Smart Calorie intake (Real Protein--FISH,MEAT,Protein Rich Vegetables, Fruits, EGG, Milk) !! Instead to 3 times a day meal eat 6 times of small portion, comprising more than required calorie to maintain!!

+ do Share your Workouts! Trick is not  making it monotonous, do different exercises each day/week/month!! 

i donno whch one u tuk bruh ..might be whey protein ..buh mega mass wrks n nt jus fr 13 days keep on taking it on alternate days

I would recommend anybody trying to Gain or Lose Weight to understand  BODY FAT PERCENTAGE (www.healthchecksystems.com/bodyfat.htm).

Healthy way is to GAIN LEAN MUSCLE and not FAT :-))