Scientific measures in the study of NEOs

First of all, scientists have to discover NEOs, which isn't an easy task, since they look like stars (at least for asteroids). Normally this is done with optical images (as photographs) or using more complicated CCD. These images allow to recognize NEOs by their motion, since they move, on the background sky, faster than stars.

As a second task, orbits of these objects have to be tracked, in order to know where the object will be in the future. To do this, normally many observations of the objects need to be combined.

Once the object has been tracked, its properties (such as dimension, albedo, etc) will be studied by photometric techniques, which include the study of light curves to determine the shape and how the NEO revolves. These techniques can be combined with radiometry to obtain more results.
When photometry is applied to different wavelengths, the technique is called spectrography. The chemical composition of NEOs is being in these last years tested in this way, examining the spectrum of the reflected light from the object and identifying the chemical elements present at their surfaces.
Instruments such as radars are also very useful to determine NEOs' orbits and to study their tridimensional shape, creating beautiful models of these objects.

Images on this page (from top to bottom):

Photograph of 4179 Toutatis (by Alain Maury and Derral Mulholland)
Animated photo of Geographos 1620 (taken by Petr Pravec)
Lightcurve of Geographos
A spectrum
NASA's Goldstone Solar System Radar photo courtesy NASA