What exactly is "1 Serving"?!

So.

My muscles have been so sore after doing 1/4 mile of lunges with a medicine ball two days ago I still walk funny. But I am still keeping up with ab workouts and doing about a mile or so of running each day.

But I feel I need to learn more about fitness and report a bit more on it, so today's topic is portion control and learning about serving sizes. Often when I grab cereal or eat a piece of chicken, I just go ahead and eat it without too much thought and figure, "hey, it's healthy, so I'm cool." But lately I've been looking at the labels and trying to figure out exactly how much I'm putting into my body versus what I perceive I am putting in there. I usually use a measuring cup, but for all the lazy college students out there, here is a quick rundown of what exactly one "portion" or one "serving" is. It's not an exact science, but it's a helpful tool.

• A tennis ball = 1 serving of an orange, apple, or pasta (1 cup)
  
• Deck of cards = 1 serving of poultry (3 ounces)
• A golf ball = 1 serving of peanut butter (2 tbsp)
• A baseball = 1 serving of cooked vegetables (1/2 cup)
• A computer mouse = 1 serving of a potato
• A CD = 1 serving of pancakes
• 6 dice = 1 serving of cheese (1 ounce)
• A checkbook = 1 serving of fish (3 ounces)

Not to say that you're going to exactly hold up a checkbook to a fish as you are cooking it, but hey, whatever works.