I used to be around 500 lbs (srs) Currently I'm where you are at now, around 300 lbs, a little less.
Before losing any weight I just didn't give a shit and I ate and drank whatever I wanted. I just felt like it was inevitable my addiction to food was so strong. Not to mention I genuinely was grossed out by anything healthy, a vegetable would make me gag. Tbh I still have a very low tolerance for these foods, but I have just gotten used to sucking it up and eating them anyways. Now at least there are some salads I like, carrots and broccoli are okay. I find it easier to eat raw, washed veggies to any that are cooked. Texture is a big thing to me and any veggie that has soft and mushy makes the flavor, which I do not like, stronger. I do eat cooked carrots because they are more nutritious. When I was at my max weight I just sort of accepted that I would die before 30. Now that I may live a little longer, I'm not sure what to do. Now I have to figure everything out career wise because I haven't died yet, how to improve the actual quality of my life and relationships, etc. lol. I'm so fucked because I survived extreme obesity.
But at first all I did was slowly cut out drinking any soda, and changing my eating habits--instead of getting Wendy's or some garbage, I started getting Subway (which is also not great for you but better than fried stuff) or salads from the fast food places. If you drink soda at all, cut it out. Has no benefit to your body at all, even a hamburger at least has protein. A can of soda has nothing of value but the taste. Over time I faded out eating any fast food at all besides very rare occasions when I have really no other option.
I did tons of cardio. At the time I had a part time job but was mostly NEET, and my job itself required a lot of cardio. So I was burning a lot of calories through that as well.
I will say along the way, I've had a lot of setbacks and regaining of weight. Don't get stressed out too much, if you gain a little bit of weight back--it's completely normal. Just don't let it discourage you enough to quit. Keep on the program, adjust it and cut more calories if you need to. But just always keep it in your mind, your soul, that you will get to whatever your goal is. I had lost some weight back in higschool, but gained it all back (and then some) after just accepting this is a fact of my life. Keep at it, you will almost certainly have bad days, but don't let one day screw up all the work you did. If you have better willpower than me hopefully you avoid any bad days. Holidays and things always make it difficult, sometimes I even just leave the room if there's a lot of bad foods around.
Eventually you will most likely reach a plateau. You will probably have to make some more adjustments, and increase your exercise even more or decrease your calories. I weighed much more than you ever did, so maybe it's even more difficult in my circumstances. But the body wants you to gain it all back, so for me I have to just learn to live with a certain level of hunger. Drinking water before and after meals helps.
I never followed any sort of strict guidelines, but now that I'm not losing anymore I will probably have to start tracking everything. At first I was just using common sense, if you know it's bad for your body and won't help you reach the goal, don't eat it. But I didn't actually track carbs or anything at first. You may need to do this sense you were never as big as me, as fat as I was it was shockingly easy to lose the first 100 pounds.
I'm not even close to done, you're starting at where I've got to after 2 years of changing lifestyle. But with the setbacks I've had and regains, I never lost sight of the goal, that's the most important thing, keeping the right mindset.
Now I'm focused more on bodyfat than pounds lost though, that's really what's most important.