Keep track of what you consume, even liquids.  Yes, even that little square of chocolate counts too.  You would be amazed at how quickly calories, fat, sodium, and carbohydrates can add up for your daily allotment.  There are apps that can do it for you, like My Fitness Pal and MyPlate.  Once you start logging in your food choices (all of them), the app will tell you how much fat, calories, carbs, cholesterol, protein you have consumed.  It will gauge if you have stayed within your limits or if you have exceeded them.  After a week of tracking you will be more comfortable with making healthy choices quickly.  Think of it as a teaching tool.  Once you learn how to eat healthy you will never have to go on a diet again.

(Please note:  When calculating how many calories a day you need, make sure you are realistic with your exercise level so the app calculates correctly.  1100 calories a day is not a healthy amount for a person who works out).