A radar functions by sending out a beam of radiation and recording the time, intensity, and Doppler shift of the echo that is scattered or reflected back to the radar.
In addition to precipitation, various types of false echo include ground clutter, anomalous propagation, radiation sources, birds and insects, and clear air. Not all false echo is bad; clear air return is useful for detecting things like fronts and outflow boundaries.
Because the radar beam is higher above the ground when it is farther from the radar, the distribution of echo and winds may tell you more about the vertical variation of reflectivity and velocity than about their horizontal variation.
Forecasting precipitation using the radar is mainly a matter of extrapolating the motion and evolution of the precipitation. You are encouraged to take a broad view and look at the evolution of the precipitation pattern rather than following individual cells, which tend to have short lifetimes.