Eating healthy doesn't mean that you have to cut all unhealthy foods out of your diet (I for one love pizza), but just to make sure you don't eat excessive amounts of it, try adding some fruit and veg in there too.
The recommended 5-a-day is a great guideline to go by, and you can have them as snacks or incorporate them into meals.
Although there is nothing wrong with having and enjoying a large meal, eating too much food on a regular basis can be detrimental too your health.
Try to limit portion sizes, or make sure you have a way to burn off the calories.
Eating breakfast is incredibly important and is not something that should be missed. Your body hasn't eaten anything since the night before and so your metabolism has slowed, eating breakfast wakes up your metabolism and gets it functioning.
Concentration levels won't be as high and you're putting yourself in risk of fainting (even if its never happened to you before).
Research suggests that eating breakfast aids weight loss, and helps you to be able to manage your lunch sizes (as you're not hungry enough to eat an entire cow).
Make sure you get enough of your beauty sleep. I've talked about sleep in some of my previous posts, so I'll refer you to them: How Much Sleep do we Need and How to Relax Before Bed.
Drinking lots of water is great for your health and can help boost your metabolism, which can help burn more calories. Water helps flush out toxins and also reduces the chance of illnesses and diseases later on in life (e.g. Kidney Stones etc).
Loads of people love to bathe in the sunlight and to get a tan, but the suns UV rays are harmful and can cause skin cancer and accelerated ageing of the skin. Wearing sun cream (or sun-screen, whatever you like to call it,) can help prevent this.
Exercise is one of the key things to do to get in shape. Of course if you're eating more calories than you're burning, then you're still going to be gaining weight. The trick is to burn more calories than you intake, which although sounds simple, does take some commitment on your behalf.
Snacking is such an easy thing to do for all people of all ages. If you're having a problem with snacking, then I'll refer you to a previous post of mine: How to Stop Snacking.