[netsharc]

I'm going to modify my keyboard to generate em-dash when I input "-"...

[rockercoaster]

Option+shift+dash, on a default English Mac keyboard. Easy to remember—"modify [option] the dash [dash] to make the biggest common form of it [shift]", or else you can think of it as modifying the underscore (shift + dash) to sit higher on the line (with option).

[froober]

That works well until the following doesn't compile

int x = 1 — 2;

[SAI_Peregrinus]

  #define — -

fixes that issue for C.