The use of density modification to improve the electron density map has become a very popular technique in protein crystallography. This method is not a "direct method". To obtain an interpretable electron density map using a density modification technique, a set of good initial phases is required. Naturally both the phase angle and the figure of merit attached to each reflection affect the results of a density modification procedure. Thus an appropriate estimation of the figure of merit is also important in this procedure Most importantly, our experiences show that having a good initial set of phases is most important in obtaining good results. Thus a simple-minded patient search for good heavy atom derivatives is the most important step in protein crystallography apart from the purification and crystallization of proteins.