What most people are failing to tell you is. You need to find out how much food your body needs, not how much it wants. If you gained 10lbs, you are obviously over-eating.
If you take a plate of food out, only eat half. You need to control yourself, and don't let your appetite take control of you.
Seinfeld even said it himself. Sometimes he likes to ruin his appetite, why? Because he gets 6 of them a day! So remember if you think you are "starving", you aren't, just put a little bit of food aka "energy" in your body.
Stop eating before you go to bed, if you eat before you go to bed, what do you think happens to all those calories? This is where the famous "beer gut" comes from, as drinking alcohol does not make you gain weight, but the food that you tend to eat after does.
Cut out as much nasty stuff like sweets, pop, popcorn, ice cream, cake ETC. Drink water/Eat Fruits and vegetables. although I tend to eat sweets sometimes, but it is very important you keep it to a minimum, if at all. You can still lose weight, however remember you are slowing down the weight loss process.
Anyways, good luck! Remember eating(for the rest of your life) less is the first step to maintaining a lower weight.
Now about Exercising:
People are saying that exercising is the only way to lose weight. Not only is that incorrect, it is not needed. Although it is healthy and you should. Losing weight can be done with by just the above method, however exercising does burn calories so of course it is better than sitting on the couch if you want to lose weight!