For the last couple of weeks, I’ve been traveling and been a house guest at a number of friends’ houses. It is, of course, the only good reason to have friends in the first place. Otherwise, you have to listen to them tell you about their prospective gall bladder surgery. 

And right before I was a guest, I welcomed house guests into my own home, which is the unfortunate price you have to pay for later sponging off them.

I am, therefore, an expert in house-guesting, and I’ve learned there are some rules you must follow to make house-guesting work, including making believe you are interested in talking about their problems and not yours.

Here are the other rules:

Do not use your host’s shampoo even if it’s right there on the shower shelf and yours has been confiscated by airport security because it was larger than 3.5 ounces and you didn’t place it into a color-coordinated, Homeland Security-approved, American Idol-runner-up plastic baggie. The shampoo on the shelf may be for colored permed hair and you will end up looking like macaroni and cheese.

Don’t open the refrigerator at your host’s place looking for a late-night snack and take out what you think is broth from the back of the fridge. If you’re lucky, it’s over-priced coconut water.

If your guests ask to help out around the house, let them, particularly if they want to rotate the mattress in the master bedroom, which you last did in 1987.

Understand there will not be enough room to spread out your stuff because the closet in the room you’re staying in will be jammed with your hosts’ son’s Little League uniforms, an extensive baseball card collection, all his school report cards and a half dozen geometry textbooks even though their son is now 35 years old and a hedge fund manager who rarely plays Little League.

Bring your own toothpaste. Your host probably only has cinnamon-flavored-teeth-whitening-organically-grown-free-traded eucalyptus toothpaste. It will taste like broccoli.

Your guests — or your hosts — will not have the same sleeping habits as you do. They will keep you up later and wake you up earlier than you are used to. Some early mornings, they will force you to do yoga.

The place where you are staying will have an incomprehensible remote control for the TV and when you try to use it, you are likely to erase their favorite movies and several entire seasons of “Mad Men” and force them to watch the Weather Channel all the time even when there’s no weather.

When you are a house guest, always bring a gift, to thank your hosts for their generosity. I recommend coconut water.