This really depends on your own needs, and health. Eating Healthy is really about finding a good balance, and still enjoying your food.
I know for me I cut out oils that were not good for you and started using more of olive oil and Coconut oil. Suprising awesome. I added alot of veggies and cut out bread and most products made with yeast. In addition I started eating meats that were cage free, or grass fed. I would suggest starting small though.
One thing I recently tried was adding almond flour instead of normal pancake mix to the my diet. I love it and there is a variety of things you can do with it. Including Blueberry pancakes.
There are many ways to start with healthy eating but it depends on what you need what are your goals. You should eat more fruits, vegetables and whole grain & stop eating processed food. Stop drinking juices that contain sugar & eat more fish.
I always thought that I would start on Monday or the new year but I realized that I have to start the moment I think about it. Then you will be successful. You don't have to wait for a certain time.