We are preparing an experimental search for weakly interacting massive particle (WIMP) dark matter using cryogenic germanium detectors. These detectors measure both the ionization and phonons produced by particle interactions in the substrate. The ionization measurement uses low drift fields, approximately equals 1 V/cm. The phonon measurement is made using neutron transmutation doped (NTD) germanium thermistors. Simultaneous detection of phonons and ionization allows us to discriminate between electron-recoil and nuclear-recoil events which gives a powerful method for isolating possible WIMP events (nuclear recoils) from background gamma ray events (electron recoils). Recent work on our understanding and optimization of these detectors will be presented.