10.8 How do I produce C-XXX with my keyboard?

On terminals (but not under X), some common “aliases” are:

C-2 or C-<SPC>

C-@

C-6

C-^

C-7 or C-S--

C-_

C-4

C-\

C-5

C-]

C-/

C-?

Often other aliases exist; use the C-h c command and try <CTRL> with all of the digits on your keyboard to see what gets generated. You can also try the C-h w command if you know the name of the command.