1. Eat 6 small meals through out the day
This is one of the most important things if you want to increase your weight. Eating small meals throughout the day will help your body to absorb the nutrients properly and digest the food properly.
2. Portion size
There is a common myth that fats are not good for health. There are certain type of fats those are good for your health. You must eat a variety of food at the same time and your diet should include good sources of fats like Fish and Linseed oil.
Calculate your daily calorie requirements and make sure you exceed those limits if you want to gain weight. The ratio for Carbohydrates, Protein and Fat should be 4:4:2 respectively. This will help your body get all essential nutrients.