A lot people say that they are useless. Which they are direct from the factory. What a lot of people don't realize is that the fogs are aimed incorrectly from the factory (Full down). With proper color conversion (ideally "selective yellow") and properly aimed they are very useful.
Keep in mind fog lights are only used for inclement weather such as moderate to heavy rain, fog, and snow. They shouldn't be left on at all times. It always surprises me how many people leave their fogs on during clear nights. Properly aimed fog lamps cause a lot of glare to oncoming traffic. So please mind others safety.
To properly aim them follow the instruction: Daniel Stern Lighting Consultancy and Supply
There's a vertical adjustment screw on the back of the fog light assembly.
Selective yellow conversion can be done by either applying a yellow film over the lens and/or by painting the assembly with metallic clear yellow paint.
As for bulb the stock bulb should be enough. Remember fogs are only supposed to light the foreground (First 10-20ft in front of the car) so you can see road lines and immediate road obstacles. Brighter bulbs usually inhibit fog usefulness by increasing back reflection.