The final accuracy of a radioactivity measurement can depend to a high degree on the quality of the radioactive sources used. In this paper the most important source preparation technique for radionuclide metrology is described in detail, namely the quantitative preparation of solid sources by drop deposition. Different steps in this source preparation procedure are described, such as preparation of source supports, preparation of dilutions, quantitative drop deposition by the pycnometer method, mass determination, control and improvement of the source quality and the uncertainty calculations involved. Other source preparation techniques of special interest are briefly mentioned and the handling and storage of solutions and sources are discussed.