I am thin and people would often tell me that I should gain some weight. But if I gain weight, I want to have toned muscles and not fats.

I asked someone who has been working out for a while to give me tips on how to increase muscle mass. He told me to increase my calorie intake (but  not junk foods), then workout regularly. I do not have to worry about getting fat if I eat a lot of food, as long as I have the ability to burn these calories and turn them to muscles. It also helps to include a good amount of protein rich foods on your diet.