So I'm going to preface this by saying that I've been very fortunate on my weight loss journey including how much free time I have to dedicate to cooking, and what I've done won't work for everyone. Also I recommend not being hyper focused on weight and instead focus on being healthy.

I used to be very overweight, and was always overweight growing up. I'm 6'3" and at my highest in my mid 20's was 330 lbs. I basically didn't pay attention to what I ate at all, so I ate both too much and not healthy. 8 years later and now I'm around 215, and I have much more thought and time going into how I eat.

I decided that I wanted to change that, and after research I learned a few general things:

1. If you want to have sustained weight loss you can't go on a diet - you need to change your habits and relationship to food. If you ever plan to go back to eating how you are now, you will return to the same weight and health. If you're not prepared to have a permanent change to how you eat, you're probably better off just staying the course because going back and forth can be very unhealthy, both mentally and physically.
2. Losing weight and changing habits are slow processes. It will take months or years to see significant progress, and it won't be a straight line. Because it's a permanent change there will be ups and downs along the way and over time, and that's normal and fine. For me it's been about 8 years and I'm still making slow progress, but there have been slips where I've gained 20-30 lbs back (pandemic was a bitch!)
3. My results are probably not typical. Everyone is on their own journey and dealing with their own hurdles, so don't compare your results to someone else's. Progress is progress, no matter how small. And improving your health is absolutely progress, even if the number on the scale doesn't change.
4. EXERCISE. But not for the reasons you think. You will never be able to outrun a bad diet, you just don't burn calories that fast while exercising. But it boosts your energy, mood, and for me also helped a ton with leveling out my hunger levels. It's also probably the single biggest thing you can do to improve your health.

Sorry about the novel before I go into the question, but I've seen a lot of unhealthy mindsets and advice and I think it's important to share that even with success stories there is struggle and it's a constant battle and lifestyle change. It's not easy, and anyone telling you differently is selling something.

So, on to what I do!

Best advice I've heard boils down to "Eat food. Not too much. Mostly plants."

Don't try to follow fad diets. I haven't seen any good reliable science that supports any super strict diet. The day to day doesn't matter anywhere near as much as the week to week and month to month. Don't beat yourself up because you went to a party and indulged, or spent a holiday week with your family and went a little overboard. But if you're doing that every week, it's going to have an impact.

For me what worked was a combination of counting calories and substituting foods. I started by logging everything I ate without trying to change anything, just to get a baseline (this was VERY illuminating, it's shocking how easy it is to eat 3000-4000 calories when you're mostly eating junk food). Try not to judge yourself here and make sure to log everything you eat, but don't try to go insane accuracy. Again, aim for broad trends not the small details.

Once you have a good baseline, figure out where you can substitute out higher calorie dense foods with lower calorie dense foods. This usually means more veggies, less junk food. The goal here is to be able to still eat until you feel full, but to decrease the total calories. You want to be able to feel full, because if you're constantly hungry you likely won't be able to maintain it long term. A good strategy is to identify some foods that you like that are low calorie density that don't require any prep. If you're hungry and it's not meal time, eat those. My foods were carrots, apples, and celery. I can eat as much of those as I want until I'm not hungry and it won't have a huge impact on my daily calorie intake.

And honestly, that's kind of it - rinse and repeat. Experiment with new foods and recipes that are healthier and keep looking for substitutions you can do. Like stew or pasta sauce? Increase the amount and variety of veggies you throw in. Start to learn which foods are high calorie density and which ones are lower. Look to eat a variety of foods to improve overall nutrition.

If you are lucky enough to have the time, learn to cook more. A lot of processed foods have a bunch of sugar in them, and that increases calories a ton without making you feel more full. Cook in big batches so most of the time it's still quick and easy to eat healthy. Get a few recipe staples that you can cook without thinking or looking up the recipe to lower the effort for home cooked food. An instant pot is great for making large batches of healthy food - a beef and bean chili with tons of veggies over rice is super healthy, fairly low touch time, and you can make like 10-15 meals at a time. Air fryers are great for cooking 1-2 portions at a time of food you prepare in advance, so actual touch time is pretty low.

It's really hard at first. It gets easier over time (months and years). I'm 8 years in and these things are much more natural to me, but if I'm not actively putting thought and effort into what I eat I still skip into bad habits.

Hope this helps, and best wishes to everyone on a journey for their own health and relationship with food!