  Particle-accelerating colliding-wind binaries (PACWBs) are multiple systems
made of early-type stars able to accelerate particles up to relativistic
velocities. The relativistic particles can interact with different fields
(magnetic or radiation) in the colliding-wind region and produce non-thermal
emission. In many cases, non-thermal synchrotron radiation might be observable
and thus constitute an indicator of the existence of a relativistic particle
population in these multiple systems. To date, the catalogue of PACWBs includes
about 40 objects spread over many stellar types and evolutionary stages, with
no clear trend pointing to privileged subclasses of objects likely to
accelerate particles. This paper aims at discussing critically some criteria
for selecting new candidates among massive binaries. The subsequent search for
non-thermal radiation in these objects is expected to lead to new detections of
particle accelerators. On the basis of this discussion, some broad ideas for
observation strategies are formulated. At this stage of the investigation of
PACWBs, there is no clear reason to consider particle acceleration in massive
binaries as an anomaly or even as a rare phenomenon. We therefore consider that
several PACWBs will be detected in the forthcoming years, essentially using
sensitive radio interferometers which are capable of measuring synchrotron
emission from colliding-wind binaries. Prospects for high-energy detections are
also briefly addressed.
