Actually taking IR photos is pretty simple, but getting good results is largely a matter of trial and error. It's best to set your camera to monochrome (black and white) mode, because otherwise the IR filter will give everything a red colour cast. Use the 2-second self-timer too, to reduce the possibility of camera shake.
It's hard to predict how different things will look in infrared, so the best option is to try it and see. The main source of infrared light in our environment is of course the Sun, so it's best to try IR photography on a bright sunny day. Generally anything that is very hot or reflects infrared will appear light, while cold things or objects which absorb IR will appear dark. Foliage reflects a lot of IR, so grass, trees and other plants will appear very bright. Man-made things such as concrete buildings, roads and other urban objects will usually appear unchanged, since they reflect only part of the IR. Water is usually cold and absorbs IR, and so will normally appear very dark. A clear blue sky will also appear dark, but clouds will appear quite bright.
Depending on your camera, you may need to process you pictures a bit when you get them home. Because you are shooting with only a limited amount of light the pictures may lack contrast, but you can correct this using the Levels tool in Photoshop or most other image editing programs, or simply use Automatic Contrast Enhancement, also a feature of most good image editors.
The resulting pictures have an unearthly, dream-like quality to them, and look strangely beautiful. Subjects that work well include anything that is already slightly spooky, such as old castles, Victorian graveyards and ruined buildings. Try it for yourself, and have fun!