If you are going to store information on a USB stick (perhaps as a backup), either use a USB stick with hardware encryption, or else encrypt the drive before you store the information on it.
That way, if you lose the drive, or it is stolen, the finder or thief cannot access the information on it.
Use an alternative whenever you can, such as a file transfer platform.
No, this is not a euphemism.
You have no idea what security might (or might not) be in place on the other computer, whether it is infected by a virus or dormant ransomware, and so on.
If you absolutely have to transfer something to someone else’s computer via USB (perhaps because the files are just too large to transfer via a file transfer platform in a convenient manner, or else you are in a situation with no Internet access):
It’s not kind to the environment, but the price of small USB sticks makes them disposable.
Even if it is coming from your friend, or a trusted colleague, do you know what security they have on their computer? Do you know what state their anti-virus protection is in?
Get them to transfer you the file some other way, and take precautions when opening it.
Don't use USB sticks given away at events. If you need a USB stick for something, buy one from a vendor you trust.
USB sticks might seem like good giveaway items at conferences, but it's a bad idea, as it encourages poor security practice. If you want to make files away, host them on your website or some other sharing service, and give out the link.
Nothing found on the ground or in the carpark or “left over” in a meeting room.
Yes, it might suck to feel that you could be a good Samaritan and return someone’s vital information or backup of family photographs, but you have absolutely no idea as to what is on that memory stick, and there’s a chance, perhaps even a strong chance, that it might be an attack.