I probably avoid some scams by:

(1) Not wanting to buy stuff on the street, regardless of what it is or even if it is free. If someone wants to give me some coats or something, I'm never interested. I typically own a coat and if I want to buy another one, I will go to a store.

(2) Not wanting to get some special deal that someone is offering. I will make every effort to to research the best deal at home before the trip, but if someone offers a special train ticket or something like that, I'm not interested. I want to pay the best available regular/special fare officially available.

(3) Not wanting to meet people. If someone approaches me in a country where I am not familiar with things, I typically would say "sorry I can't help you" and walk away. If I want to meet people, I will travel with an organized group to that country.

(4) When in doubt, I quickly walk away and walk faster than the approaching person.

(5) When approached, always say "no" regardless of what the question is. Well, not always, but much of the time. Some innocent questioners have received this answer when it wasn't warranted. Perhaps even a recent person in Buenos Aires who asked "may I ask you something".

(6) Avoiding taking taxis...anywhere, or at least have the hotel arrange for one.

(7) Never carrying my wallet in a reachable space.