When looking to change your diet, being aware of what you are consuming is step number one. Tracking meals, to some degree, whether that be for nutritional values, calories, macros, or other numerical values can put some context into your food and water consumption. This can be done with paper and pen, however, the ease of an app may make you more inclined to stay consistent.
Below, are some top-rated apps that may be useful for diet tracking:
MyFitnessPal
MyNetDiary
HealthyOut
Cronometer
MyPlate Calorie Counter