Know your subject. Whether it is insects, circuits or flowers.
Learning a little about your subject before you photograph it will intuitively get you better results. For living things knowing their habits for insects or growth seasons and cycles for flowers and other plants will increase the time you can spend photographing them and getting them at their peak.
Create and use a check-list. Listing out all the equipment you think you will need before going out to shoot will greatly lessen the chances of leaving important pieces of equipment at home and ensure that you will have the right equipment for the subject. Don't forget things like extra memory cards and batteries.
Use a Tripod. This is the easiest way to insure that your photos will not have any blur or camera shake. Photography in the macro range of a lens magnifies the effect of any movement of the camera and lens while the photo is being taken. Also, using a tripod can make you work a little more slowly and methodically, increasing your chance of getting better photos.
Because macro lenses have very shallow depth of field (shallow area of focus) very close up consider using F/11 or F/16 to get most of small subjects in focus. Conversely, if you only want a small area in focus, say just the head of an insect, use a wide aperture of F/2.8 or F/4.
Use the appropriate macro lens and keep the right distance. Many insects are skittish and will run if you get too close with a lens. A 50mm macro lens focus at 1:1 (life sizes) at about 5.5 inches. A 100mm macro like the Tokina AT-X M100 PRO D will achieve 1:1 at 11 inches, leaving more room to work and not invading the insects “space”. This will increase your chances of photographing an insects natural behaviour. In some cases it might be necessary to leave even more distance and crop in to the image in the computer.
Use an arm with a soft clamp to steady flowers. One end of the arm or other device mounts on the tripod and the other hold the flower in place. It is VERY difficult to get an in-focus macro photo of a flower that is swinging in the breeze.
Consider using a macro flash to control the direction of light and to light the subject very evenly. Marco ring lights create a catch-light in insects eyes and can also be held over the subject to create even light from above.
Consider using a small fabric diffuser panel (a scrim) to soften harsh direct sunlight. Several companies make ones that have a wire frame and “pop” out and fold up to be very compact and light-weight. They come is sizes from 10x10 in. Up to almost any size you want. These are available from PhotoFlex and other companies.
If you want to take macro photos but cannot afford a macro lens like the Tokina AT-X M100 PRO D, consider using either Kenko Extension Tube Set or Hoya Close-Up Filters. Extension tube maintain the original quality of the lens while forcing it focus closer than normal. Close up filters act in a similar way. using either extension tubes or close up filters will lock your lens into only focusing at a very close distance. To focus farther away you will need to remove them from the lens.