A friend of mine went to Tokyo and, after work, went out for dinner & a drink. He woke up about 6 hour later. Many thousands of dollars on his charge card. So, watch out for Mickey Finns. For you younger readers, that’s a drugged drink. Sort of like a date rape drink. If you didn’t pour your own drink out of the sealed bottle, don’t drink it. If they get cranky, just tell them it’s an “old american custom”.
Cabs are another major source for muggings, kidnappings etc. Do not let a stranger select a taxi from the airport for you. Actually, that probably applies at the hotel too. Be sure the cab driver is licensed and her/his face matches the license photo. If there is no photo or license, be careful.
Once you get into the cab (or a rental car for that matter) be sure to *all* the doors, A favorite stunt is to pop a door, grab your bag, backpack or purse & run.
Finally, a frequent trick is a fake (or crooked) cop. If a policeman tries to arrest you, demand to see some ID and use your cell phone to contact a friend.