Recently I had a requirement where I had to enter special characters in a German Windows Operating System (Virtual Machine) with US English Keyboard. The characters were \, /, @ etc. While unicode code points were an obvious solution, I realized that there was a better one in the form of AltGr and another key.
The ALT GR key is on the right side of the keyboard on some non-U.S. keyboard layouts. ALT GR is equivalent to the CTRL+ALT key combination, and you can use it with other keys to enter additional characters.
Here is the list which I found in Microsoft site for German. Check out the page for other languages like Dutch, Greek etc.
For keying in other characters like -, / the easy way was to use the keyboard numpad.