Id use a relay to avoid frying your switch.
Heres a really simple diagram i found, as i am not at my house to scan in the diagram i made.
The switched signal wire is where ever you want to get your power from. i chose a open slot on the fuse box that shot off with the ignition.
Also if you use a toyota fog light switch the prongs do the following. (I think)
top= ground
middle=hot (signal)
bottom= to relay