There is one, and only one, certain truth when you go to Las Vegas (or, really, any casino): You’re probably going to lose. Outside of that fact, however, lies a mixture of rumors, conjecture and superstition. Some of those are perfectly harmless, while others could end up costing you money. Here are four of my favorites:

“Play the Slot Machines on the Aisle”

Books could be written about the mythology of slot machines, from a system to beat them (There isn’t one.) to the machine that is “hot” or “ready to hit” the jackpot (none of those, either). When it comes to slot machines, correlation does not equal causation. Slot machine results are determined by a random number generator that matches a combination with a result every time you push the button. Pushing the button a certain way while holding your left elbow on a Tuesday after Thanksgiving will not get you better odds, no matter how many times your mother-in-law’s best friend’s son has won that way.

My personal favorite slot machine urban legend is that you should always play the machine on the aisle, or one where a lot of people will see you. As the legend goes, lots of people will see you win and want to play themselves, so the casino places the machines with the highest payout where the most people will see them.

This is one of those myths that could end up hurting you if, for no other reason than they know so many people believe it that the casinos could put the worst machines on the aisles, knowing they will get the most play. In truth, however, they’ll place the “tightest” machines anywhere that they believe that the most people will play them. I have had more than one casino executive tell me that the most profitable machines are often the ones right in front of the bathrooms and the restaurants, where people will wait for others.

“Casinos Pump in Oxygen to Keep the Players Awake”

Casinos do lots of things to keep people from leaving their casinos. They serve you free drinks. They take away the clocks. They make it hard to find the exits.

But I don’t care what Mario Puzo says, they do not pump oxygen in to get you giddy or keep you awake. While they have experimented with pumping in pleasant scents, similar to any establishment that is trying to sell you something, the cost and flammability of the oxygen would not be to the casino’s benefit.

You may actually feel better when you get off the casino floor, but that has less to do with extra oxygen being pumped in and more to do with the air being fresher away from the cigarette smoke.

“It’s Illegal to Count Cards”

Gamblers often try to gain an advantage in blackjack by “counting” cards, or keeping track of how many high and low cards have been dealt, and adjusting their bets accordingly. Doing it correctly does generate a long-term mathematical advantage for the players, so casinos don’t want the good counters on their floors.

But it’s not illegal. You can’t go to jail for counting cards. The vast majority of jurisdictions can boot you from the casino and/or make your life so miserable at the table (constant shuffling of cards, deep cuts on the deck, etc.) that it’s simply not worth your time, but they won’t call the police, unless they ban you from the property and you decide to return. In that case, you still can’t get convicted for a card counting offense, but you would be guilty of trespassing.

Card counting may not be worth your time even if you were able to to do it without any impediments from the house. Keeping track of numbers through six or eight decks, while determining how to maximize your bet is even more complicated than it sounds. I have no doubt that most customers who try to count cards fail at it and end up losing even more money than they otherwise would have.

“Prostitution is legal/illegal in Nevada”

What happens in Vegas stays in Vegas, right? What they don’t tell you is that it could be you that stays in Vegas, and it might not be in a bed at the Bellagio, but rather, on a cot behind bars. Sure, there are strip gentlemen’s clubs everywhere and those guys on the street corners flicking cards at you but, despite what people tell you, prostitution is illegal in Las Vegas.

But it’s also untrue that prostitution is completely illegal in Nevada. In fact, brothels are as close as an hour from Las Vegas in scenic Pahrump (and if there is a better name for a town with legalized prostitution, I have yet to find it). And that’s pretty much everything that I know about it.