If I want to put a switch on the AC current...?

[LegendBreath]

Hey,
If I want my project to have a on and off switch, can I put a simple 2 wires switch on ONE of the AC current?

 

[audioguru2]

If you are in North America then use a switch rated for the mains voltage and whatever current your circuit will have at max. Switch the mains hot wire if the plug is polarized.
For a few cents more you can get a two-pole switch to switch both wires which is safer.