Cut and open commands?

[saneman]

I would like to redefine cut and open to: C-x and C-o regardless of the 
built in definitions. But I cannot redefine cut:

(global-set-key "\C-x" 'kill)

when I select some text and press C-x I just get:

symbols function definition is void:kill

And what are the function called that opens a new file?


Currently I have to press C-space to start a mark in the text that I can 
use to select some text. Is it possible to just redefine to shift 
instead of C-space?