I have a great deal of weight to lose as well. The best advice I can find is don't make yourself miserable. The key to long term weight loss in large amounts is long term behavior modification. You can't do something for a week or a month. Because of this, many of us eat foods we don't like, give up whole food groups, or force ourselves into unhappy exercise, then can't keep it up - because no one is going to do something that makes them miserable for the long term.
Be honest. Honest about the foods you will eat, honest about the exercise you can do, honest about what you can commit to. If something is not pleasurable, you won't do it. That does not mean you lack will power - it means you are human, and the brain has evolved to keep you supplied with dopamine. So pick out foods that you enjoy eating, pick out the nutrient dense ones and eat those in small amounts.
No one wants to do it, but in the beginning you will need to weigh your food or count the calories. I recommend starting at 2,000. You can lose a lot of weight on 2,000 calories, and if you work all day you will need them to keep your energy up. You will be tempted to negotiate calories (I can eat this today if I don't eat this tomorrow....ect) This will not work. You really need to stick to your guns on the 2,000. I once calculated that even 200 calories a day (once slice of cheddar+one apple) over 2,000 every day will actually cause you to gain.
Also, the calorie killer is eating out. Even if the calories are on display, most of the time most chain restaurants don't measure out the amounts of sauces and oil exactly when cooking. It may say 500 calories and really be 1,000. If you want to stick to 2,000 you need to make your own food.
Find out if you are insulin resistant - if you have a muffin and a glass of orange juice do you go into an exhaustion coma? This means your body produces insulin differently, and you will need to make sure you are eating protein and fat with your carbs to slow down your insulin response.
Choose an easy exercise that costs no money, and you enjoy. I suggest walking. Walk an hour outside of your usual activities. Go at a comfortable pace. Not slow and meandering, not fast.
Also, sometimes you will have a shitty day, and go over your calories. That is life. The key is that the next day you get back on the horse and don't use it as an excuse to throw the whole week away.
If you can do this for a year, you will lose at least half the weight. It is going to be annoying because you are going to want external validation from the scale, and that will end up happening slowly when you want it to happen quickly. If you are very big, you will also have to wait for the "Have you lost weight?" exclamations that feel so good.
But if you can do it - eat foods you enjoy in the right amounts, eat nutrient dense foods, make sure your meals have fat, carbs and protein in every meal, walk an extra hour every day, it really will work.