In my opinion one of the most interesting areas of photography is macro. With a good macro lens, the detail that can be revealed in subjects like flowers and insects is truly amazing. I use the Canon EF 100mm f2.8 macro lens, when attached to the 400D body it is the equivalent of 160mm. This allows for a greater working distance so you do not disturb the subject. A lot of compact cameras have a 1cm macro mode, the problem with this is that the camera has to be 1cm away from the subject, this can be very difficult to achieve without interfering with the subject matter.
If possible I always try have my camera tripod mounted and use a remote cable release to minimise camera shake and the risk of a blurred image. Depth of filed is always an issue with macro photography. So it is important to set a high aperture F stop number (small aperture) this will mean more of the image will be in focus. This will result in a slower shutter speed, hence the need for stability. Using a larger aperture (smaller F number) allows more light into the camera, but this makes only a small portion of the image sharp with the rest blurring out. Having said that, a lot of macro shots using this technique have a great deal of impact, and the area that is sharp really jumps out at you.
Even using a small aperture (high F stop number) on a macro lens will still only give you a few millimeters of depth of field in front and behind your focus point. I often find that using autofocus on the lens results in an image with an unintentional focus point. I usually set my lens to manual focus, that way I can control exactly which point of the subject I want to be sharp.
No matter how stable your camera, you cannot rely on the subject remaining motionless, flowers for example, if shooting out in the field, will be subject to movement by the wind, the only way to minimize this movement is to create some kind of windbreak. Insects on the other hand are not so easily controlled! The only option is to try and create a faster shutter speed for your camera to hopefully freeze any motion, you can do this by altering the ISO setting of your camera, uping the ISO will in effect make your cameras sensor more sensitive to light, therefore the higher the iso, the faster the shutter speed, do remember though that the higher the ISO, the quality of your image will suffer.This effect is know as noise. Failing that you could always try using the flash of your camera, but this can often bleach out detail or result in uneven lighting. After research on the net, the best option for macro flash photography is using an external ring flash, this will illuminate your subject evenly.
This article only scratches the service of macro photography, the main thing is to get out there and practice, I myself am a beginner, and I find that searching the internet is an invaluable way of improving your technique and knowledge. I also subscribe to a camera techniques magazine which is full of useful information for shooting a huge range of subject matter.