By increasing your calorie intake, you're body will require more food to feel satisfied - but this process takes time. For the first month or two you may feel perpetually full and have no appetite at all. Gaining can be quite a shock to the system.
It also helps to distract yourself while eating - mindless snacking while watching tv, etc. encourages overeating.
Eating as fast as you can also helps because the brain doesn't register fullness for 20 min or so