At the hotel

Hotels, especially of the four and five star category are normally extremely safe; providing you with a safe in the room and at the reception area, security guards hiding around the place, and cameras that can be as much your friend as your enemy. But things still can happen so here are a few tips to avoid your valued possessions from taking a walk:
If the hotel has in room safes use it and keep all your valuables in there.
However, if the safe is electronic, wipe the touch keys down before operating it with a damp cloth, and then dry it before entering your secret code. Try to do this every time you use the safe.
Also after you have keyed in your code and closed the door firmly locked on the safe press all the other keys /numbers that do not make up your code, and press them firmly. Doing this may set off a small alarm from the safe but it stops quickly and no one will pay any attention (!!).
The reason to do this is because certain hotels have caught their own hotel staff placing, a light oil residue or powder on to the touch keys that shows them when using a certain light what numbers were pressed. They were managing to open the safe, and one very clever thief was taking only 1 or 2 US$ from each room. Would you have noticed? It is not a lot but in a 400 or 500 room hotel the guy was doing quite well for himself.
Never leave valuables in soft/material bags with pockets even if they are padlocked like Alcatraz
this avoids any potential of somebody simply splitting a seam to a pocket with a knife and removing select contents. This has happened to one of our friends and he never even noticed until he went into the bag and pockets a while later.
This should also apply to luggage that you check into the airplane.
Never get drunk and invite a stranger to your room. This seems funny, I know, but better safe than sorry.