Being aware of your surroundings is key to not falling victim to travel scams, but the best travel scams are the ones you never see coming. Even seemingly-innocent interactions, like someone asking for your help or offering shelter from the rain, can inevitably lead to expectations of money -- even if money is never discussed.
Image from wonderlane.
It may sound harsh, but when you're a tourist, you have a target on your back and lots of people want your cash. Nomadic Matt explains when you should be suspicious:
If someone asks you into their shop for tea, they are going to use that as a pretext to get you to buy something and, thanks to the engrained psychological idea of reciprocity, you'll probably give in. Don't let anyone ask you to write a letter or read a postcard that their "cousin" sent to them in English/French/whatever your native language is. It's a ruse to get you into their store and wear you down. Same with letting someone put henna on your hand. Once these vendors have you, they will be relentless about you trying on clothes, buying something, or giving them money. Say "no thank-you" and walk away.
It can be tough to resist the instinct to help someone with such a simple request. Similarly, Matt notes that even the people who say things like "no money" when they meet you almost certainly will ask for money at some point, like would-be tour guides who'll stroll up to your group and offer to show you a nearby destination, or suggest a great place to eat in the area.
Just remind yourself that locals who make their living off tourist dollars (like shop owners and tour guides) want you to hand over those dollars, and some are more above-board than others, no matter where you go. Matt's tips are intended for tourists headed to Morocco, but they're good advice anywhere you may roam.
9 Ways to Stay Safe (And Sane) in Morocco [Nomadic Matt]