Take care to store, maintain, and clean the calibration standards properly. Refer to Keysight Technologies Application Note 326: Coaxial Systems Principles of Microwave Connector Care for reference information.
Calibrate the system with the sample holder connected to the cable (or waveguide adapter) at PORT 2 for best results. If this is not possible, calibrate at the connection interface to the sample holder. For a coaxial holder, this is at the end of the test cables that attach to the sample holder. For the waveguide holder, this is at the waveguide ends of the coax-to-waveguide adapters.
Set frequency before calibration
Calibrate the system manually, from the front panel of the network analyzer
Calibrate with the sample holder in place if possible (see Sample and Sample Holder Considerations for details)
Minimize cable movement after calibration
Use a sample holder with the same length as the sample to avoid holder losses.