These are the ones that I plan on keeping the rest of my life:
Exercise. I have to move. It doesn't mean I need to be at the current schedule but at least 2-3x a week I NEED to exercise.
Whole grains. We eat white bread only on very, very special occasions (like Christmas) beyond that we eat whole wheat/whole grains for everything.
Low Sugar Diet. When I started I went sugar free for 6 months. Now I'll eat it on occasion but I always buy single portion sizes and if we go out and get a dessert we split it amongst the three of us. At home I mostly just use maple syrup/blue agave/honey to cook with.
Lots of fruits and veggies and meat. Without thinking much about it we've cut back significantly on dairy and carbs (by that I mean bread, rice etc, not veggies/fruit) and most of our meals are composed of meat+veggies with fruit for dessert. It helps that where we live cheese is freaking expensive (as well as my favorite breads) but these changes really have changed the amount of food we consume.
I've never calorie counted consistently so mostly I just work on watching my hunger signals, eating snacks, keeping hydrated etc. I feel these are things I can maintain for the rest of my life, which is absolutely my goal.
ETA: I also had to come to accept there are certain foods I REFUSE to give up: pizza, hamburgers, and hotdogs.
Now, I'll eat less pizza and combine it with a salad or eat just one hamburger loaded up with veggies, no fries or eat hotdogs with soup but I'm still eating them and a diet without them always leads to some insane binges otherwise.
ETA2: I see others have mentioned daily weighing and that's definitely one of mine but I forgot to mention it.