I feel you. I used to be 275 lbs, dropped to 197 lbs, got hurt, shot back up to 240, and now am back down to 220 and still dropping. You've already made the first step in deciding you want to become healthier, so that's the best start. I'll share with you some things that I've learned so far....in no particular order.
1. It is a lifestyle change. There's no such thing as "going on a diet". The definition of a diet (it's a noun) is the kinds of food that you eat. Do not think "I'm going on a diet" (the verb). Your mentality should be that you want to clean up your diet by eating healthier foods and staying away from the fried, processed, fast food crap that easily available. Eating a healthy diet should be permanent. Like I said, it's a lifestyle change.
2. Keep your caloric intake on a budget. Your body needs energy to function. It gets energy from the foods that your eat. If you consume more energy than you need, then your body will store the energy as fat. There's plenty of online resources that will help you figure out what your ideal caloric intake should be and don't go above that.
3. Instead of eating 3 (or 4 or 5) large meals a day. Eat smaller meals about 5 to six times a day. Remember to stay within your caloric budget. For example, if your caloric budge is 2500 calories a day, and you eat 6 meals a day, each meal should be roughly 416 calories (2500 divided by 6). This will boost your metabolism and help you burn off the fat. Remember to keep your diet (the noun, not the verb) clean.
4. This one may sound a little controversial. But a lot of people think of their meals as this joyous grandios feast and celebration. I know people who cook breakfast, lunch, and diner by making these elaborate feasts. For example, some people I know would never consider having a sandwich for diner. Or will only eat eggs for breakfast. I once had this mentality. But I had to change it. My new mentality is that meals are for substance. I need the proper amount of carbs, protein and fats. For me, it's OK to have some egg whites, a little bit of oatmeal or brown rice, and a handful of almonds. It's within my caloric budget, simple to make, and has everything that I need. Now granted, some people can still have their grandios meals and still be within their budget, and that's great! But for me, that's too much work and I find this mentality to be more successful for me. But it's your call, and you might have to put in some work for this.
5. Plan, Plan, Plan.
I plan and cook my meals for the week. I'll cook some chicken breasts, brown rice, veggies, etc. and put the right portion into plastic bags or disposable containers. When I wake up and had my breakfast, I pull what I need for the day and put it into my lunch box for me to take to work. And at work I'll eat meals 2, 3, 4, and 5. Meal 6 I'll eat at home, and I usually cook something simple. Sometimes my job requires me to travel, and that can certainly derail a healthy diet. I take my own food with me on flights. Some foods I use are protein bars, tuna (in the sealed pouch), almonds, sandwiches. Some hotels have fridges, so I'll do a little shopping at a local store and will eat that instead of going out. In some cases it's unavoidable and I might have to eat at a restaurant. Fortunately, many restaurants have healthy option but if you're in a bind, get the less of all the evils and limit your portions. It won't be the end of the world this one time.
6. Be more active and burn those calories. Join a local gym, or pick up a recreational sport. Start walking. Then turn walking in to brisk walking. Then turn brisk walking into runs. Or maybe ride a bike, or anything that'll keep the heart rate up. To supplement
your physical actives, doing a lot of little things can add up. For example, park further away from the building when you go to work. Maybe take the stairs instead of the elevator. Also, a great workout at the gym is a great stress reliever. Whether I'm pissed off or depressed, it helps a lot and I feel so much better afterwards.
7. Don't trust your scale, because it will lie to you sometimes. If the number on the scale does not drop, it does not necessarily mean you're not losing weight. Don't use the number on the scale as your main metric. Use that in conjunction with body fat percentage and how your clothes fit. Muscle weights more than body fat. In some cases, you might gain more muscle than you lose fat. So the number on the scale might say you didn't lose any weight. But that can be misleading. For a time, I hovered around the 200 lb range, but my clothes were fitting better, and I noticed that parts of my body were looking better. I even dropped a full pant size. Take some body measurements and go by that (waist, arms, chest, neck, etc), along with body fat percentage, and your total body weight (the number of the scale).
That's all I can think of for now. It's going to be a lot of trial and error and you'll have to figure out what works best for you. Don't get discouraged, because in the long run it'll be worth it. I'm not going to lie, it's going to be tough at first. If you can survive the first two weeks, the changes you make will become a habit.
Good luck with your new lifestyle.