Don't expect to just buy a filter and be off on a nice happy IR cruise, you need to hav mastered a few fundamentals before getting anything useable from IR (Not to put you off but expect work to get anything good!):
Firstly camera and lens. Not all are capable of working with IR filters, especially true of Canon and Nikon, even more so if you use third party modern lenses. (search for info about hot spots in infra red photograpy, there's a very long list of no go lenses somewhere).
Seond, filter. Several filters available - the most common is the Hoya R72 or it's clones. Standard duotone Infra red filter, good for colour and B&W. It's around 720nm. 890nm etc are B&W only 650nm is false colour, I like it for portraits but that's it.
Third - the quirks of handling. IR focusses at different distances to normal light, AF will be fine as long as you trust it because you won't be able to see through the viewfinder at all. Manual focus lenses are a no go unless they have IR index mark, you can focus accurately from the scale and are prepared for some dud shots. (Focus then fit filter). Live view should just about let you see through the filter at big apertures.
Fourth - Processing. White Balance is very tricky to set for false colour, not so important for B&W (though it does subtly alter the image). Best Shoot Raw anyway as there will be a lot of work to do. Mst usual PP is to flip the colour channels - you swap the red with the blue normally.
That's a very quick rundown. I used to love shooting IR with my old Olympus because it woudl focus in IR just like it would with daylight and the white balance was easily set to just how I like it. However with my Panasonic I cannot get it anywhere near where I want. Sometimes it results in a good image but it's not ideal.
I use a Neewer 720nm filter and a no name 650nm filter, but only rarely for the latter as I don't much like it's results.
