If you're hungry, eat. When you're not hungry anymore, stop eating. This sounds simple, but it can be difficult to practice.
Yup, partially because processed foods have very high calorie counts, and sweetened drinks are everywhere. One of the reasons soda is such a pain is because it's so many calories for not a lot of stomach space. Switching to water, tea, etc helps. I almost never have anything except water with meals now. Kinda nice - cleans the palate, works with everything, cheap, etc.
But as an instructor pointed out, "You spent 20 years putting on that weight. It's not going to all come off in 20 days."
Eh, that's kind of a silly comparison or line of reasoning. The problem is mostly that there are a TON of calories in one pound of fat - 3500+. Calorie restriction works, it's just that because of the energy in a pound of fat, it can only work at a certain speed (dropping too many calories from your diet will result in weakness, getting sick more, etc), and that speed is a bit slower than people might hope. Let me put it this way: if your daily calorie usage is about 2000 calories and you don't eat anything for 24 hours, you'll lose well less than a pound (yes, I'm ignoring glycogen stores.)
Implementation of calorie restriction is difficult for many, yes. If you eat because you're unhappy, for example, then you shouldn't just talk to a dietician - you should also talk to a (licensed) mental health councilor of some sort. If you're snacking throughout the day or eating a massive lunch, you need a better breakfast. Etc. etc.
Everyone thinks exercise helps - and yes, it does, and you're definitely healthier and better off for it. But one of the cruel jokes about exercise is that when you do more of it, you become more efficient as a food-burning machine. People also underestimate the amount of calories burned from exercise, and above a certain level of activity, most of the calories come from your glycogen stores and carbohydrates, not fat.
Increasing activity and muscle mass helps, too, as muscle mass increase = daily calorie use increase. Everyone should do at least some sort of weight training, including-and-especially women, where weight lifting helps counteract bone density loss. Walking and cycling for transport helps quite a bit - even a 15-20 minute commute by bike is worth a decent number of calories, maybe 10% or so of your daily needs.