We discuss and compare approaches to using Auger data for semi-quantitative determination of surface compositions of Al-based quasicrystals. We have examined two quasicrystalline phases: icosahedral Al-Cu-Fe and Al-Pd-Mn. We find that sensitivity factors obtained from pure elemental standards lead to underestimation of concentrations by as much as a factor of 2.5 for the minor constituents, Fe and Mn, and to overestimation by as much as a factor of 1.2 for the major constituent, Al. Surprisingly, calibration with a crystalline phase close in composition to the quasicrystal does not necessarily lead to more accurate results. Auger analyses of fractured surfaces, which are then compared to bulk analyses, is the best option for sensitivity factor calibration. Even without absolute calibration of sensitivity factors, however, surface analysis is extremely useful for detection of secondary phases, and is superior to common bulk analysis methods.