Transcript for What Most Salespeople Won't Tell You
True confessions continues on "20/20." Now, with Dan Harris. Reporter: Between you and whatever you want to buy stands the salesperson. Immortalized in such classic movies as "Analyze that." Anyway, let's get serious. You want to buy this car or not? Yea or nay? Reporter: And used cars. Hey, I like that watch, great shoes, love 'em. So, Stan, you want to buy this buick centurion? Good choice. Reporter: And tonight, we've got three former salespeople who are sharing their secret tactics, starting with perhaps the most feared figure of them all, the car dealer. At my very worst, I was a bloodsucking salesman. Really? Oh god, high pressure. Reporter: By his own admission, ray Lopez spent 26 years as a manipulative salesman. And he says the hustle begins as soon as drive onto the lot. I've already psychoanalyzed you from the moment you got of your car. Reporter: As soon as you open your mouth, he applies a label to you, like "An easy mark", someone who needs to buy a car immediately, a "Lay-down," someone who accepts the first deal put out there, a "Researcher," who has done his or her homework, or "An analyst," someone who's all business. If you are very monotone and just give me precise answers, I immediately, I know you're analytical. So I know how to play you now. Play me? He does that by responding in the same way, giving precise answers, no extra information. They feel like they're not getting worked? Exactly. Now you're comfortable. You think that I'm your friend. Reporter: Now you're more likely to trust the final deal. But what if you're a researcher and you really know your stuff? Here's ray's come on -- You're a very intelligent person, you've done your due diligence. So we can cut out the B.S. Reporter: But that's bs too? Yes, because I'm playing up to your ego. You guys are malignant psychiatrists. Reporter: In fact, says Dan, manipulative dealers will start working you before you walk on the lot. With questionable ads like this one. Zero down, zero due at signing. We asked these car owners to squint hard enough to read the fine print. Due at least signing. So then that's confusing because you're like, wait a minute. Holy crap, is this legal? Reporter: Actually, it's not, according to the federal trade commission. The dealer agreed to take them down, though did not admit to wrongdoing. Ray says it's all about getting you into the store. Because once you're there, we're going to play you. Reporter: Ray did finally decide to change his ways. He's now the author of a book called "Inside the minds of car dealers." I knew this was going to be bad, but I am really surprised at how devious you guys are. Oh, yeah. Reporter: Okay, so that's the car dealership, but it turns out there are also dangers lurking at the mall. Women, beware of the makeover chair. The minute they sat in the chair, the amount they spent went up double. Reporter: For seven years CARA Phillips lured women into free makeovers. She says makeup artists keep adding product after product to your face so that you eventually feel obligated to buy. And if not -- Some people would actually just lie and say, oh, no, there's a minimum purchase of three items. And just hope they didn't get caught. Reporter: Management pressure to hit quotas was intense, she says. So one trick used to boost sales, convince women to pull out their current makeup stash, and then react with "The face." Look at something and be like, oh. And if you make the right face the customer will be like, what's wrong with it? I knew this wasn't right for me, and immediately they're going to buy whatever version that you have. Reporter: She also revealed that there's nothing makeup salespeople hate more than customers who don't buy anything. At one store they even used a secret code, 612, to warn one another about these looky-loos. It was like a game to come up with a way to incorporate 612 into something, oh, your train leaves at 612 today. Reporter: Not everyone needs makeup, but in this tech-saturated age, the electronics store is unavoidable. It can be a confusing place, and you assume that your geek guide knows his or her stuff, right? What are the odds that the salesperson has no idea what they're talking about? Yeah, the odds are pretty high. I've witnessed co-workers telling customers things that with such conviction that were just blatantly false. Reporter: Former saleswoman Ashley myers says the real thing to look out for are salespeople that try to talk you into buying expensive add-ons like an extended warranty. There's almost no profit margin on actual hardware, the margin on actual hardware, the computers, cell phones, TV stuff like that. Stores don't make much money on the big ticket items. That's why the prices are so low. They make most of their dough by upselling you. For example when we bought $350 laptop, we were also pitched an extended warranty, accident protection, and an antivirus program. Final cost, $609. A huge increase. You have to say I want what I want and I don't want anything else. Reporter: David Pearce, of tech website theverge says you should really just buy accident coverage for gadgets you actually carry around with you, period. And he told us the single most shocking thing we heard. It has to do with these hdmi cables you have to buy every time you get a new TV. I've tested $6 cables, I've tested $600 cables, and for every use case imaginable for an average human being, they are exactly the same. Reporter: Very long cables are the only exception, Pearce says. Otherwise, no difference. Really? Are you ready for this? Yes! Reporter: We got a group of kids to watch the movie monsters inc on side by side screens, to see if they can tell the difference in picture quality. The TVs and DVD players are identical, the only difference, is the cables connecting them. So one of them has a $6 cable and the other one has a $380 cable. That's like a total opposite. Exactly. So we want to see if you guys can see which television has the better cable. That one might be the cheap and that one might be expensive. I cannot see the difference. Reporter: This one has the $380 cable. No I guessed that one. Reporter: You were right the first time but then you changed your guess. You'd think with that huge price difference the winner would be obvious, but the results were a draw. What would you do with all the money you saved, if you could spend just $6? I'd just put it in my piggy bank. Buy a dragon. Reporter: A dragon? Dragons aren't real. Only if they were real. Reporter: Actually, depending on where you shop, the dragons may be very real.
This transcript has been automatically generated and may not be 100% accurate.