Right, to answer your specific questions:
You need to use some kind of a filter. There are several kinds of infrared films on the consumer market (Kodak HIE, Ilford SFX and Konica IR, Maco IR being the most common ones) but all are sensitive to both the visible spectrum as well as the near-visible infrared spectrum. Because of this, unless you take some steps to minimise the visible spectrum, visible light will largely shape the picture instead of IR radiation. Each film has different sensitivity to infrared wavelengths, and has different cut-off points of the visible spectrum.
Depending on what you're after, you can use a 25A deep red filter with most of these films which gives a good infrared effect with the minimum of fuss. Visibly opaque infrared filters can also be used to increase the infrared effect, because they further decrease the visible light reaching the film. But because these are visibly opaque, expensive, and specialised, they tend to be less popular. However if you have a digital camera, particularly those with reasonable IR blocking filters, then you may need one. I use one with my D1 series and they work great.
In you use a proper infrared filter (i.e. opaque to visible light) then you cannot use normal film. Or you can, but with VERY long exposures. While I haven't tried this, in theory this should yield the same result as using a dark red/brown filter, but with even longer exposure times than using a conventional red filter - i.e. there's no practical reason for using IR filters with normal film (aside possibly from as a makeshift high powered ND filter).
Hope that helps.
