As Barry mentioned, extension tubes are an excellent way to do close
up photography. Extension tubes coupled with true macro lenses are even
better, but probably THE best set-up is a true macro lens and a bellows
extension device rather than extension tubes. A bellows gives a greater
range of adjustment than extension tubes and can be locked in place for
rock solid steadiness. BTW, the best way to ensure stability in the
set up is to use sand bags on a table-top rather than a tripod. Use a
shutter release cable, and, if your camera can do it, raise the mirror
to elimnate vibration from the mirror return mechanism.
Close up bellows are widely available from camera supply outfits.
J. Del Col