National Pizza Day is celebrated each year on Feb. 9. But before you head out for a celebratory slice, you’d be wise to take a few precautions.

After all, among the many reputable slice shops in your neighborhood, it’s likely that a few of those pizza purveyors are pushing less-than palatable pizza. And while it’s easy enough to look up any restaurant’s reviews online, determining the quality of a pizza often comes down to gut instinct, especially before you get that pizza into your aforementioned gut.

NEW JERSEY DECLARES ITSELF 'PIZZA CAPITAL OF THE WORLD,' TWITTER TAKES ISSUE

To that end, Fox News reached out to Mark Bello, the owner and operator of Pizza School NYC, for help in determining a disgusting slice before handing over your hard-earned cash.

By his own estimation, Bello — who has demonstrated pizza-making at the James Beard House, and was named a “pizza expert” at the Food & Wine masters series — has tasted thousands of pizzas, both in the U.S. and abroad. And when it comes to trying out a new slice shop, he tells Fox News to beware of five red flags.

#1. Too-good-to-be-true deals

Bello says consumers should immediately be wary “if the place is trying to sell you on the quantity of the pizza over the quality of the pizza.”

That doesn’t mean the pizza is necessarily bad, however. It’s just the first of a few factors that point to poor pizza.

CLICK HERE TO SIGN UP FOR OUR LIFESTYLE NEWSLETTER

#2. Sorry-looking slices

Quality pizza is always going to look appetizing, but it’s not always going to look consistently the same, even between slices from the same pizzeria. And it should never be too “pale,” Bello says.

“If the outer crust resembles the rim of a Styrofoam cup in geometry, uniformity and pale color it’s likely going to taste like the outer rim of a Styrofoam cup,” according to the expert.

#3. The wrong ingredients

Depending on the size of the pizzeria, some shops may have their ingredients on display, or at least in view of patrons (e.g., cans of tomatoes, bags of flour, cheese, etc.). So if you sense one of the makings is amiss, take your tastebuds elsewhere.

“For example, often pizzerias have their bags of flour stored in view of the customer — if they say ‘bromated’ and/or ‘bleached’ that’s not good,” Bello says, referring to flours that have been treated to change their pigments, help develop gluten or strengthen the dough.

#4. It’s praised as great ‘drunk food’

Good pizza should taste like good pizza all the time — not only when you’re inebriated.

Or, as Bello advises, never go out of your way “if the overwhelming recommendations you hear for the pizzeria in question emphasize ‘it’s best if you go there at 3 a.m. when you're really drunk…’”

FOLLOW US ON FACEBOOK FOR MORE FOX LIFESTYLE NEWS

#5. Their cheese slice stinks

So the pizza seems slightly questionable, but it looks halfway decent and you can’t see the ingredients. In that case, stick with a single cheese slice: It’s the ultimate indicator of the rest of the menu, according to Bello.

“If their classic cheese and sauce slice is bad (that’s the telltale slice to try first at any pizzeria) move along,” the expert advises.

CLICK HERE TO GET THE FOX NEWS APP

Mark Bello is the owner and operator of Pizza School NYC. Since 2010, the company has shared its knowledge of pizza with over 50,000 students. For more visit Pizza School NYC’s official website