The handful of patterns worth recognising

Most people you deal with are honest. These are the recurring exceptions, and they mostly rely on you being rushed.

A word of proportion first: the overwhelming majority of transactions while travelling are straightforward, and treating every vendor as an adversary is both unpleasant and inaccurate. But a small number of patterns recur worldwide, and they all rely on the same thing — you being hurried, unfamiliar with the notes, and unwilling to make a scene.

The recurring ones

• Short-changing. Change counted quickly, one note light, in a currency where you are still slow at reading numbers. Count it before you walk away, visibly and without hurry.
• The note swap. You hand over a large note, it is returned as a smaller one with "you gave me this". Say the value out loud as you hand it over.
• The "no change" round-up. A genuine problem in many places and occasionally a tactic. Carry small notes.
• Rigged or absent taxi meters. Agree the fare first where meters are not standard, or use an app that fixes the price.
• Dynamic currency conversion at the terminal. Not a scam, but it costs more than any of the above. Always decline it.
• The friendly-rate street exchange. An excellent rate offered informally, delivered as a fast count in a currency you do not know. Use a bureau.
• Card skimming at standalone ATMs. Prefer machines attached to banks, cover the keypad, check for anything loose on the card slot.
• Menus without prices, particularly for seafood sold by weight. Ask before ordering.

The habits that cover nearly all of it

1. Know roughly what things cost, so a wrong number feels wrong immediately.
2. Count change before leaving the counter.
3. Say amounts out loud as you hand them over.
4. Carry small notes so "no change" never forces a decision.
5. Agree prices before the service, not after.
6. Be willing to be slightly awkward for ten seconds.

The first of those does most of the work, and it is why knowing the rule of thumb matters more than any app — including ours. A price that is wrong by a factor of ten should feel wrong before you have finished hearing it.