Our testing indicates that the choice of competent cells is critical. We recommend the use of high efficiency chemically competent cells such as NEB 5-alpha Competent E. coli (High Efficiency) (NEB #C2987). The reaction can be added directly to the cells without any dilution, although further dilution of the reaction mix may improve transformation efficiency. However when using high efficiency chemically competent cells from some other vendors, if you did not get any colonies, we recommend a 1:4 dilution of the reaction prior to transformation. For transformation into all high efficiency electrocompetent cells, including NEB's, we recommend a 1:3 dilution of the reaction.