The first thing that you need to do is to start drinking more water
. This will replace other drinks that are not as good for you. Some theorize that drinking cold water actually burns a few calories since the body warms it up. This is a great habit for long term health as well.
Do your best to avoid fried foods. These are loaded with fats and calories and have basically no nutritional value. If you cut these out of your diet, you can cut huge calories for your diet and help lose some weight.
While not all fast food is bad, start avoiding it as much as you can. Not all this food is bad but much of it is loaded with salts, fats, and excess calories. Start making your own home meals versus eating out as often especially if it's fast food.
Try to replace one snack during your day with healthy, fresh foods. These would be simple things like vegetables and fruits. These are loaded with nutrients and fiber which you need while replacing something that is much higher in sugar or calories.
Find ways of moving throughout the day. This could be as simple as taking the stairs or finding an outdoor hobby like hiking. If you find things that you actually enjoy, it will be much easier to continue to do them over the long run. You can burn quite a few calories through some simple exercises that you do on a regular basis.
You don't have to do all these things at once. Be sure to work on one until you have it then start with another discipline next.