I presently have a switch in a bathroom with 3 14/2 cables coming into the switch box. The switch only controls a light for the medicine cabinet. All the whites are connected together. Two of the blacks with a pig tale are connected to the bottom screw of the switch. The other black is connected to the top screw of the switch. When I turn the switch on, the light for the medicine cabinet goes on. I would like to add and wire a exhaust fan in the bathroom. The exhaust fan would be a fan only. I think I can do this in the following way. I would add a switch for the fan only. I would run a 14/2 cable from the fan to the new switch, and add the new white wire to the other white wires. Then connect a pig tale on the old switch (for power) and connect that to the bottom screw of the new switch. Then connect the black wire of the 14/2 to the top screw of the new switch. What I'm basically trying to do is connect to the hot black wire of the old switch and pig tale that hot wire into the new switch for power to the fan. Is this the right way to do this ?:confused:

I think that will work but wished you had used a better descriptor than "top screw." You need to tap the incoming hot wire prior to the cabinet switch. All whites do go together. Do you have a bare ground going to the fan? You need to ground this unit. I would also check to see if this circuit is on a GFI, if not install one. All bath and bedrooms need GFI or ARC faults.

Take a look at the double switches, i.e. 2 switches in the same space. Double switches use an outlet cover rather than a switch cover. Each switch occuppies the spot an outlet would and has a horizontal movement rather than a vertical. They are very useful in adding a switch without expanding the box, i.e. the hole in the wall. The decora line even has a triple switch.

Good luck,
Jimmy