Here is a list of techniques that we use to model planetoids:

Lightcurve inversion The lightcurve inversion technique is used to find an object's rotation period, its shape and spin-axis orientation.

Radiometry Radiometry is a powerful technique to derive size, albedo, and thermal properties from thermal infrared measurements.

Occultation Occultation is a powerful technique to derive the size and cross section of a small body in a direct way.

Radar Radar is an active and experimental technique to retrieve information about asteroids.

Direct imaging Direct imaging techniques are related to measurements by large ground or space telescopes or by using data from interplanetary mission.