You’ve decided you want to eat ‘better’. What does that mean though ? Here’s what you can do in increasing order of difficulty:

1. Be restrained, measured and cut back on how much you eat out. Be very selective in where and what you eat when you eat out. 
2. Cut back on liquid calories. Coffee, tea, juices, softdrinks, kombuchas, alcohol all contain energy. Lots of it and it’s easy to underestimate how much. Be measured. It helps to go with beverages that use erythritol and non-nutritive sweeteners. Recent fuss over non-nutritive sweeteners is overblown. Dosage and context matters. 
3. Include 3-4 cups of cooked non-starchy vegetables in a day. Make an effort to include 70-80 grams of protein from lean, thoughtfully prepared foods. Restrict the amount of oil you use on a daily basis to prepare your food. This takes a little effort but can go a long way. 
4. Log your food everyday. A log gives you perspective on how much you eat and what you eat. Couple this with a rough sense of how much energy you need in a day. 
5. Detailed meal planning. Know exactly how much and what you eat in a day. Measure what you eat. Even when you stray from the plan, do so in a measured manner. Needless to say, very few take this approach all year round. But few can argue with the results of this meticulous approach. 


Bonus points :
1. A good vitamin and mineral supplement is a good insurance policy. 
2. Protein supplements have received some bad press. But like with all things in life, you need to pay for quality and be picky. There are good brands and bad ones. There are better products and worse. Pick wisely.
3. Pick an algal or fish oil for omega-3. No other foods give you appreciable amounts of it.