What's the quickest and most effective way to gain weight?

Eat healthy foods: That are high in calories. Eat six meals per day. Work on strength training to build your large muscle groups. Work out w heavier weights w fewer repetitions. Sleep at least 8 to 9 hours/night. Hydrate well w water. Foods to help w healthy weight gain: almonds, cashews, pecans, sunflower seeds, flax seeds, walnuts, hummus, avocadoes, granola, trail mix, dried fruits, extra virgin olive oil, can.