Carrying out high resolution, 3D hydrodynamic simulations with radiative transfer already included, allow us to create realistic "mock observations" or "synthetic images" for a given instrument & telescope combination. These mock observations can be compared with already existing real data, or prepare for future observational proposals. We use them to understand how massive forming planets could be observed with the different instruments, how the planet-disk interactions look like on various wavelengths and what planet-generated features we can observe with the current & near-future instrumentation. I review our findings for near- and mid-infrared, sub-millimeter and radio wavelengths, and identify what are the best wavelengths and instruments for hunting for forming planets.