Hi!
I have never kept a count of my daily intake of calories. I am not organized enough. Plus, when I start to pay closer attention, food seems more like a medicine to me and I don't "enjoy" eating, which is bad when you are trying to gain weight. I have had success in my past gaining weight by eating the same- just increasing my supplement consumption, ex: Ensure Plus. I usually eat a full meal, then I force an Ensure Plus down for the extra 375 calories. I drink about 6 a day when trying to gain, 4 a day to maintain. I never drink them before a meal, the fill me up so I can't eat. Easier to chug down afterwards.
I have also had success with Weight Gainer shakes from GNC. Each mixed shake contains about 2500 calories. Good luck with your weight gain!