If you are interested in nutritional portions, the do go to mypyramid... those are the science based portions.
Keep in mind that not all fat is bad. Learn the different fats, and realize that some fat is important. For example, using an olive oil based vinaigrette without sugar, on your salad is better for the nutritional value of the salad than using a low/no fat dressing. The compounds of the low/no fat dressing actually block the body's absorption of the nutritional goodness of the salad. So do some research.
The portion sizes on purchased containers (of anything) are advertizing promos first, nutrition last. The value of that information is to tell you how much of the container you can eat for an ingestion of how many calories, grams of fat, protien, carbs, ect. Again, learn to truly read the label. They are not as clear cut as those manufacturers would like you to think.
All food has a recommended (nutritionally based) portion. If you are not counting serving portions of whatever you are eating, you are ingesting an unknown quantity of calories.
Not all fruit is as healthy as is often thought. Some fruits are actually to be avoided if you wish to keep your blood glucose levels stable (important for everyone not just those diagnosed with diabetes).
So, go with the science based portions. Research fats, and label reading. And know your body. What works for another person most likely will NOT work for you. That's why there are so many conflicting messages out there about weight loss, and nutrition. Each person's body responds differently to the intake of nutrients based on the variables that are in place for that individual.
The start of the whole thing is to understand the basic principles, and then learn what works for you.
Good luck to you. Being healthy through eating wisely is a great thing!