Get super clear on what you want to accomplish before you dive into your resolution. What does eating "better" really mean to you? Do you simply want to eat more fruits and vegetables or are you interested in trying a completely new type of diet?
And most importantly, figure out what end goal is going to motivate you the most to sustain these changes long-term. It might be losing weight, improving your cholesterol or lowering your blood pressure.
You'll be a lot better off when you find your "why" first and then follow that with a concrete action plan.