• Counting calories: Calculate your basic calorie requirement.You want to know how to  gain weight ? You will have to increase your calorie intake. Add 500 calories per day to your current requirement. Those who work out or are physically very active, have a higher energy requirement. If such is a case the calories consumed should be greater than the amount of calories you burn.
• Eat more: The most common answer to your question how to gain weight. Everybody will ask you to eat more. Yes, you need to increase the quantity of food you eat, but at the same time you have to make sure you are eating healthy. Eat five to six meals a day. Avoid skipping any meal. Knowing how to gain weight involves consistent eating. Increase your portion size. If you eat 2 chapatis, then start eating a 3rd one. Take a second scoop of pasta, or add two bananas to your bowl of cereals.

• Choose calorie–dense foods:  Choose foods that are higher in healthy calories. For example choose to eat corn, potatoes or peas instead of carrots and cucumbers. Eat a banana, custard apple, chikku or mango instead of a watermelon or orange juice. Peanut butters and  cheese makes a calorie-dense yet nutritious spread for your sandwich. Read food labels for the serving size and the calories.
• Adopt good habits: The repetitive advice to increase your food intake does not mean you start eating unhealthy, fried, sweet or junk food for that matter. Adopt healthy habits. Eat your meals on time. Do not skip any meal, specially breakfast. Whatever you eat at breakfast is better absorbed and utilized by your system. So don’t forget to take a handful of nuts everyday along with good quality protein like toned milk and boiled eggs. Maintain a 2 hour window between each meal so that you can feel he hunger and eat better quantities.
• Add more liquids: You may be thinking how to gain weight with liquids. But drinking appropriate quantity of water or other liquids will help you in flushing all the waste products accumulated after digestion of those extra calories you ate. Drink water or juices. If you dislike drinking water, choose on flavored water , apple juice, milkshakes , smoothies etc. Specially if you are working out, the body needs that extra liter of water.