  We give an overview of ongoing searches for effects motivated by the study of
the quantum-gravity problem. We describe in greater detail approaches which
have not been covered in recent ``Quantum Gravity Phenomenology'' reviews. In
particular, we outline a new framework for describing Lorentz invariance
violation in the Maxwell sector. We also discuss the general strategy on the
experimental side as well as on the theoretical side for a search for quantum
gravity effects. The role of test theories, kinematical and dymamical, in this
general context is emphasized. The present status of controlled laboratory
experiments is described, and we also summarize some key results obtained on
the basis of astrophysical observations.
