I either use program mode, and let the camera body select the shutter speed, or use fully manual mode, and adjust the exposure by moving toward the light source until the desired degree of over or under exposure is predicted by the metering system. Exposures are in the range of a second or two. No tripod is needed, because the whole duplicator assembly, including the slide, is a solid tube.
Some filtration has to be used to compensate for the light source.
The best thing about this technique is that you can study the frame through the viewfinder and manipulate the exposure and filtration at leisure, with a reasonably wysiwyg interface. The outdoor technique It's also possible to use that ansi-standard light source, the sun. The problem with this technique is that the color of sunlight is quite variable, so getting the correct filtration is harder. Use the same setup every time, including approximately the same time of day and weather conditions. Film It's definitely worthwhile to use slide duplicating film, unless you actually want the contrast of your slides to increase.