In order to ensure the reliability of research results obtained in very low temperature fields, it is important that very low temperature measurement is traceable to the internationally agreed the Provisional Low Temperature Scale of 2000 (PLTS 2000). The PLTS-2000 is defined by the relationship of 3He melting pressure pm to temperature T2000 in the range of 0.9 mK to 1 K and provides four intrinsic fixed points on the melting curve. In order to realize the PLTS-2000, it is necessary to cool 3He at melting pressure down to the possible lowest temperature using a nuclear demagnetization cryostat. This cryostat must be capable of working reliably and continuously over long periods of time during ultra-low temperature experiments. In this article, we give information about low-temperature techniques for realizing the PLTS-2000 based on our experiences of designing and constructing in-house ultra-low temperature apparatus.