A healthy diet consists of whole grains, low-fat dairy and proteins, omega-3 fats (avocado, fish, olive oil etc.), fruits, vegetables, beans, and nuts. The way these foods are combined are up to the individual preference and taste. A combination of protein and carbohydrates has been shown to keep blood sugars even and keep people satiated longer (string cheese with crackers, peanut butter with apples, etc.).
Some people do better having small meals throughout the day, while others severely misjudge how much they intake at each sitting. Therefore, it is better for them to eat three square meals a day. However, it is recommended to have 40% of your overall caloric intake come from carbohydrates, 30% from protein, and 30% from fats. It has been shown that those who keep a food journal each day are more likely to stay focused on their dietary goals.
A minimum of 30 minutes of exercise five times a week is recommended by the American Heart Association. This can be done in small segments throughout the day or all at once. Having a group or workout buddy helps many keep motivated and builds accountability. Likewise, seek activities that you enjoy.