I don't recommend counting calories, because the makeup of the food is much more important. I tell my patients to aim for proteins and carbs to be about the same, by the end of the day. If you take in 100g of protein, total carb should be about the same. Obviously, not all carbs are metabolically equivalent, so as much of your carb as possible should be dietary fiber, and minimize the simple sugars as much as possible. If you avoid crunchy carbs, sweets, and white starches, you should be doing pretty well. Stay away from liquid calories, like milk and juice, and eat fresh fibrous fruits as snacks, like apples and oranges and peaches.
Limiting fat to roughly 30% of calories is also a good rule of thumb to follow.

Portions are a funny thing, because it is so variable from one person to the next, and it's why weight loss surgery is so popular, as it limits portions. The best thing to do is to eat smaller meals (I put all meals on a bread plate instead of a dinner plate) every 2-3h. Scheduled snacks work much better than random grazing, and you will find that you eat less at meals when you eat more often. The afternoon snack is particularly important, as it helps to keep you from overheating at nighttime, when your metabolism is slowest.

Good luck,
Dr Dan