Here’s the one thing you should do immediately when you enter a hotel room

Good night, sleep tight — but first, make sure the bed bugs won’t bite.

The first thing most of us do when we walk into a hotel room — most likely after a long day of travel — is the wrong thing, travel experts say.

Don’t flop on the bed and turn on the TV, according to those in the know — get under that mattress and perform a bed bug check, a quick and easy process that could save you a world of hassle later on.

“I have two really good friends who have gotten bed bugs in New York [hotels] before,” said HuffPost Senior Editor Caroline Bologna, who spoke about the subject on HuffPost’s “Am I Doing It Wrong?” podcast, co-hosted by Raj Punjabi and Noah Michelson.

“It doesn’t matter how nice the hotel is ― they’re not attracted to grime,” Bologna said.

Bed bugs crave “warmth, blood and carbon dioxide,” according to the EPA, and enjoy feeding on the blood of sleeping humans, who provide all three of those things to the hungry little monsters.

A guide published by the NYC Department of Health and Mental Hygiene, aimed at stamping out the pesky problem, describes the craven critters as “about the size of an apple seed,” saying that they’re “big enough to be easily seen, but often hide in cracks in furniture, floors, or walls.”

And how do they get into a hotel room in the first place? Easy — they hitch a ride, on clothes and in suitcases.

Bed bugs have become a global phenomenon, even interrupting Paris Fashion Week last year —  French officials were warning of a “widespread” outbreak in public spaces, referring to the problem as a “scourge.”

Currently, the Big Apple ranks number two on a new worldwide list of shame released by pest control company Orkin. Another Orkin study found that eight out of 10 hotels had bed bug problems in just one year.

Fortunately, it’s easy to avoid letting the problem ruin your next trip to the City of Light, or anywhere — take the thirty seconds or so to sweep the places in a hotel room where they might be lurking, before you settle in.

“They like upholstery — just look at the sheets,” said Bologna. “Just peel back one of the corners of the bed, look at the seams of the mattress… just check. Check anything upholstered. Look at the headboard. Look at the chairs. If you don’t see anything, you’re probably totally fine.”

Feel like being even more careful?

“People who are really cautious — like my friends who have had bed bugs — put their suitcase in the bathtub… just not on upholstery,” Bologna said. “Most hotel rooms are carpeted, so just don’t have your bag on carpeting.”

Should you be unlucky enough to find the uninvited guests in your room, don’t wait a second to tell management — complaining of bug bites after checkout is far less effective than having the hotel handle the problem (and maybe even upgrade you for your troubles) at the start of your stay.

But still, Bologna warned, make sure to distance yourself from the problem adequately.

“If you decide you don’t want to leave the hotel but you want to switch rooms, don’t move to an adjacent room because that would be likely to have the same problem,” she warned.