I found two USB sticks on the ground. Now what?

Disconnect from network. Boot from CD. Do not mount HDD.

Plug in USB drives, mount them and poke around.

Why look at the content? I can understand that you are curious, but the content of those drives is none of your business. If you lost a drive, would you want others to look at the content?

Leave some notes in the area where you found them or bring them to the lost property office if you have one.

It could be full of nanites that are going to crawl into your computer and turn it into the master computer for the super-secret Tristan da Cuhna nuclear program. :)

All kidding aside, with the possibility that it could have some form of malware, government secrets, terrorist documents, data used in identity theft, illegal pornography, or child pornography your best bet is to turn it over to law enforcement in whatever jurisdiction you found it in with as much information about where you found it as possible. Leave it to them to figure out what to do with the USB stick.