Get rid of all the bad stuff at home. That's what I had to do.
Then I bought tons of fruits of veggies (and still do every week) and learned a lot of ways to cook foods that were low in cal but very filling.
I also don't starve myself all day and wait till the evening like I used to- when I did that I'd be ravenous by the evening and stuff myself- NOT good.
I try to eat at least 1000 calories during the day by the time I get home- then eat a dinner and snack that combined is 500 calories or less.
Today for dinner I'm having a taco salad with reduced fat sour cream and using salsa for dressing. So it's lots of lettuce, tomato, and then some meat, a bit of cheese, and some sour cream and salsa- it might be higher end on calories but I have been craving it and before I'd just eat like 6 tacos! So definitely an improvement from before.
Don't do it all at once either- gradual changes- like cutting out more junkfood, then stop buying it, then buy fruits and veggies you like and try a few easy recipes, then try some new veggies and fruits and other recipes, with time you'll come to enjoy the good foods and stay away from the bad- I don't snack or eat as much junk food as I did before
Oh and drink a lot of water- I try to get in 8 cups a day