I have been asked by the powers that be at Moviefone to write little behind-the-scenes stories about movies. They apparently want me to be their "expert" on such matters.

An expert is loosely defined by Wikipedia (a completely unreliable, non-expert source) as "someone who is recognized as an authority in his or her given field."

The problem: I am not recognized as an authority in my given field. In fact, I am often not recognized as even being in my given field.

I was at Starbucks the other day, and a man waved at me and said, "I can't believe you're here!" I, of course, thought he was amazed to be seeing a famous actor standing in line for a latte with all the common folk. I was wrong. It turns out that he thought I was the barista who had recently been fired for getting high in the backroom during work hours. He couldn't believe I had the cajones to show up again.

So, in accepting Moviefone's offer to write a semi-regular column, I graciously declined the role of "expert." Instead, I suggested a far more accurate title: The Best Expert Moviefone Could Find.

And so, in coming months, I will share with you a glimpse of weird and true happenings on movie sets -- everything from dealing with difficult stars and producers to getting blown up by special-effects people.

Our first topic: snacks on set.

Food is not just food when you work in movies and TV. Seasoned actors know to expect two very different versions of food: catering (which provides meals) and craft services (which provides snacks).

Meals are almost always preferable to snacks -- for a reason. A few weeks ago, I did a part for an upcoming episode of 'The Defenders,' a CBS show starring Jerry O'Connell, and took this photo of the craft-services table -- an image that might as well be captioned "Typical Nasty Craft."

And yet filming makes you hungry, so graze we must. Upon first glance at the snack table, an experienced actor goes through a million mental calculations and applies the same type of calculus a bear uses when he looks at a berry bush.

But real actors don't check out the actual food. Instead, we look at the crew person running the craft-services table. In an instant we can tell the quality of the snacks by taking note of three qualities about the craft-services person.

1. The stomach
The same rule applies to craft-services people as it did to Michelle Pfeiffer in 'Scarface': Don't rely on your own supply. Only it's rarely enforced. The size of the crew person's stomach is usually in direct proportion to the yumminess of what's on the table.

A skinny craft-services person likely means that the best the set has to offer are wasabi-covered chocolate balls from Trader Joe's. They will be virtually inedible and will make you crap fire.

2. The tattoos
Lightening bolt tattoos on a man's calf will always mean there will be jelly donuts. I don't know why, but it's true. I don't make these things up.

3. The gender
Portly or not, I prefer a man providing the snacks. Quite often, a woman running craft services will mean deviled eggs and, occasionally, sushi. Not bad, in theory -- but eggs and the sushi are time-related snacks. Very dangerous. No one ever died from eating an old jelly donut.

Anyway, my best craft-services experience to date: 'Glee' – there were trucks of food and basically unlimited M&M's.

The worst: 'My Father the Hero' – it was just carrot sticks floating in a bowl of water, and bubble gum.

All I know is that Jerry O'Connell used his years of experience to avoid the tuna and instead go for the breadstick on 'The Defender' set.

Stephen Tobolowsky is an award-winning character actor who has appeared in over 200 movies and TV shows. His podcast, The Tobolowsky Files, is absolutely worth your time, and you should totally follow him on Twitter.