1 cut out snacking and/or extra eating, especially in the evening or late.
2 portion control. My go-to is cutting portions/portion control. Most of us (except Steve who's the same size and weight that he was in HS as he so frequently posts
) eat far larger portions than we need to. So eating smaller portions is key. Of course, what's often the case, at least for me, is that you finish your portion and there's just a bit left, not enough to save as a leftover, but you don't want it to "go to waste" so you finish it. Well, you either have to learn to save it or throw it out. You can throw out a little food in the interest of improving your health.
If you really want to ramp up your game
3 Fasting, either intermittent or more. The easiest is probably something like, get up, go to work, and don't eat anything in the morning (black coffee is fine) or during the day while you're at work, then eat a normal (not super-sized) dinner. Carry and have tons of water with you throughout the day. Drinking lots of water will make it easier to not eat. You'll also pee like a pregnant diabetic race horse because of the increased intake and because fasting causes some sort of diuretic-like function to kick in. If you REALLY want to kick things up a notch from there, kick your fast up to 36hrs. Eat a normal dinner one night, then don't have anything but water and/or black coffee the entire next day. Then on the 3rd day you can have breakfast (or eat whenever your first normal meal of the day is).
Most folks are unlikely to go for 36 hour fasts, but the 24 hour (dinner, then skip breakfast and lunch) is a bit easier, especially if you're busy at work. Key (at least for me) is having plenty of water to drink which helps stave off feelings of hunger due to an empty stomach.
Fasting is all mental (except maybe if you're diabetic or have some sort of medical condition).