The best way to shoot IR is with a modified camera, that way you are free to handhold your shots, compose through the viewfinder and focus with AF/liveview. However this requires the infraref filter to be removed and replaced with a visible light blocking filter. You are looking at $300 or so for the conversion, and it's permanent.

However there is a very easy way to dabble with IR without the cost or risk of modifying your camera! By placing a visible light blocking filter (erroneously referred to as an infra-red filter) over the lens you only allow IR lens into the camera. However due to the Camera's own infra-red blocking filter very little of the light gets through. So you need to use a long exposure (30 seconds or so) and a tripod.

You also have the problem of not being able to see through the lens with the filter on (the filter blocks visible light after all!) so you have to keep taking it off to focus and compose. Focus will be slightly off as IR focusses at a slightly different distance so you need to be aware of that (bracket your focus or stop down for more depth of field). You'll have to set the exposure by trial and error also.

The advantage compared to film however, is that you get instant results and your failures don't cost you anything so you are free to fine tune the settings as much as you like.