I'm trying to wire an exhaust fan to an bathroom light switch; how do I go about doing this project. The existing light switch is a single pole, and I assume I will need to install another double box for two (2) switches - one for the existing light and the other for the NEW exhaust fan. Please help; specifically, I would like to see how I connect the power for both light and exhaust fan switches in this new dual box. Thx. TomCT

I attached a diagram for three switches, imagine there is only two, and run one two wire cable (with ground) up to the new fan and connect per the diagram.

See if this helps, if not get back with any additional questions.

If you are lucky, when you remove existing switch, see if it is single gang mudring, in
4" X 4" box, if so, you could get 2 gang mud ring, overlay on existing single gang, draw lightly, remove drywall taking care not to go out of the line, install 2 gang mudring.
Install 2 devices, Regular 2 gang wall plate will cover. May need stacked if three devices.
If you are to open wall. Put in three gang box. Can have individual control of each.
Dimmers?